29 |
30 |
31 |
32 |
33 | )
34 | }
35 | }
36 |
37 | export default App;
--------------------------------------------------------------------------------
/app.js:
--------------------------------------------------------------------------------
1 |
2 | /**
3 | * Module dependencies.
4 | */
5 |
6 | var express = require('express')
7 | , http = require('http')
8 | , path = require('path')
9 | , bodyParser = require('body-parser')
10 | , favicon = require('serve-favicon')
11 | , logger = require('morgan')
12 | , methodOverride = require('method-override');
13 |
14 | var app = express();
15 |
16 | app.set('port', process.env.PORT || 3000);
17 | app.use(favicon(__dirname + '/public/images/favicon.png'));
18 | app.use(logger('dev'));
19 | app.use(bodyParser.urlencoded({ extended: false }));
20 | app.use(methodOverride('_method'));
21 | app.use(express.static(path.join(__dirname, 'client/build')));
22 |
23 | if (app.get('env') == 'development') {
24 | app.locals.pretty = true;
25 | }
26 |
27 | // The "catchall" handler: for any request that doesn't
28 | // match one above, send back React's index.html file.
29 | app.get('*', (req, res) => {
30 | res.sendFile(path.join(__dirname+'/client/build/index.html'));
31 | });
32 |
33 | http.createServer(app).listen(app.get('port'), function(){
34 | console.log("Express server listening on port " + app.get('port'));
35 | });
36 |
--------------------------------------------------------------------------------
/client/src/components/Header/index.js:
--------------------------------------------------------------------------------
1 | import React, { Component } from 'react';
2 | import { Link, NavLink } from 'react-router-dom';
3 |
4 | import './style.css';
5 |
6 | class Header extends Component {
7 | render() {
8 | return (
9 |
10 |
25 |
26 | )
27 | }
28 | }
29 |
30 | export default Header;
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/README.md:
--------------------------------------------------------------------------------
1 | Node.js Bootstrap Express React Starter Template
2 | ===
3 |
4 | A quick and easy Node.js + [Express](https://expressjs.com) + [React](https://reactjs.org) template project, using Twitter [Bootstrap](https://getbootstrap.com) 5.0 and React Router for creating a simple single page application.
5 |
6 | Also available for [Pug](https://github.com/primaryobjects/Node.js-Bootstrap-Starter-Template).
7 |
8 | 
9 |
10 | ## Usage
11 |
12 | - Clone repository.
13 | - Open a command prompt, navigate to the folder, and enter: `npm install`
14 | - Navigate to the folder `client` and enter: `npm install`
15 | - Next, run a build of the React client by entering: `npm run build`
16 | - Launch the node server by navigating to the root folder and entering: `npm start`
17 | - Browse to http://localhost:3000
18 |
19 | ### Development Usage
20 |
21 | - Navigate to the folder `client` and enter: `npm start`
22 |
23 | This will run the React client app.
24 |
25 | You can make changes to the pages in `/client/src/components` and see them update live.
26 |
27 | ### Legacy OpenSSL Provider
28 |
29 | If you receive an error: `export NODE_OPTIONS=--openssl-legacy-provider` use the following [steps](https://stackoverflow.com/a/69699772/2596404):
30 |
31 | - Linux
32 | ```
33 | export NODE_OPTIONS=--openssl-legacy-provider
34 | ```
35 |
36 | - Windows
37 |
38 | ```
39 | set NODE_OPTIONS=--openssl-legacy-provider
40 | ```
41 |
42 | - PowerShell
43 |
44 | ```
45 | $env:NODE_OPTIONS = "--openssl-legacy-provider"
46 | ```
47 |
48 | ## Contents:
49 |
50 | - client/src/index.js
51 | - client/src/App.js
52 | - client/src/components/Header/index.js
53 | - client/src/components/Footer/index.js
54 | - client/src/components/Home/index.js
55 | - client/src/components/About/index.js
56 | - client/src/components/Contact/index.js
57 | - client/src/components/NotFound/index.js
58 |
59 | ## Editing Pages:
60 |
61 | Edit `client/src/components/Home/index.js` to add your content to the Home page. The default contents include:
62 |
63 | ```js
64 | class Home extends Component {
65 | render() {
66 | return (
67 | <>
68 |
Home
69 |
Home
70 |
71 | )
72 | }
73 | }
74 | ```
75 |
76 | ## Author
77 | Kory Becker http://www.primaryobjects.com/kory-becker
78 |
--------------------------------------------------------------------------------
/client/public/service-worker.js:
--------------------------------------------------------------------------------
1 | "use strict";function setOfCachedUrls(e){return e.keys().then(function(e){return e.map(function(e){return e.url})}).then(function(e){return new Set(e)})}var precacheConfig=[["/index.html","c52346cb33a7eae30731fe09b8bf7828"],["/static/css/main.cacbacc7.css","214eac7d9453fa4dbe07c4ea75d9e557"],["/static/js/main.521cf01a.js","00dcf8db4676f4d1a78112ae3ed2b6e1"]],cacheName="sw-precache-v3-sw-precache-webpack-plugin-"+(self.registration?self.registration.scope:""),ignoreUrlParametersMatching=[/^utm_/],addDirectoryIndex=function(e,t){var n=new URL(e);return"/"===n.pathname.slice(-1)&&(n.pathname+=t),n.toString()},cleanResponse=function(e){return e.redirected?("body"in e?Promise.resolve(e.body):e.blob()).then(function(t){return new Response(t,{headers:e.headers,status:e.status,statusText:e.statusText})}):Promise.resolve(e)},createCacheKey=function(e,t,n,r){var a=new URL(e);return r&&a.pathname.match(r)||(a.search+=(a.search?"&":"")+encodeURIComponent(t)+"="+encodeURIComponent(n)),a.toString()},isPathWhitelisted=function(e,t){if(0===e.length)return!0;var n=new URL(t).pathname;return e.some(function(e){return n.match(e)})},stripIgnoredUrlParameters=function(e,t){var n=new URL(e);return n.hash="",n.search=n.search.slice(1).split("&").map(function(e){return e.split("=")}).filter(function(e){return t.every(function(t){return!t.test(e[0])})}).map(function(e){return e.join("=")}).join("&"),n.toString()},hashParamName="_sw-precache",urlsToCacheKeys=new Map(precacheConfig.map(function(e){var t=e[0],n=e[1],r=new URL(t,self.location),a=createCacheKey(r,hashParamName,n,/\.\w{8}\./);return[r.toString(),a]}));self.addEventListener("install",function(e){e.waitUntil(caches.open(cacheName).then(function(e){return setOfCachedUrls(e).then(function(t){return Promise.all(Array.from(urlsToCacheKeys.values()).map(function(n){if(!t.has(n)){var r=new Request(n,{credentials:"same-origin"});return fetch(r).then(function(t){if(!t.ok)throw new Error("Request for "+n+" returned a response with status "+t.status);return cleanResponse(t).then(function(t){return e.put(n,t)})})}}))})}).then(function(){return self.skipWaiting()}))}),self.addEventListener("activate",function(e){var t=new Set(urlsToCacheKeys.values());e.waitUntil(caches.open(cacheName).then(function(e){return e.keys().then(function(n){return Promise.all(n.map(function(n){if(!t.has(n.url))return e.delete(n)}))})}).then(function(){return self.clients.claim()}))}),self.addEventListener("fetch",function(e){if("GET"===e.request.method){var t,n=stripIgnoredUrlParameters(e.request.url,ignoreUrlParametersMatching);(t=urlsToCacheKeys.has(n))||(n=addDirectoryIndex(n,"index.html"),t=urlsToCacheKeys.has(n));!t&&"navigate"===e.request.mode&&isPathWhitelisted(["^(?!\\/__).*"],e.request.url)&&(n=new URL("/index.html",self.location).toString(),t=urlsToCacheKeys.has(n)),t&&e.respondWith(caches.open(cacheName).then(function(e){return e.match(urlsToCacheKeys.get(n)).then(function(e){if(e)return e;throw Error("The cached response that was expected is missing.")})}).catch(function(t){return console.warn('Couldn\'t serve response for "%s" from cache: %O',e.request.url,t),fetch(e.request)}))}});
--------------------------------------------------------------------------------
/client/src/registerServiceWorker.js:
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1 | // In production, we register a service worker to serve assets from local cache.
2 |
3 | // This lets the app load faster on subsequent visits in production, and gives
4 | // it offline capabilities. However, it also means that developers (and users)
5 | // will only see deployed updates on the "N+1" visit to a page, since previously
6 | // cached resources are updated in the background.
7 |
8 | // To learn more about the benefits of this model, read https://goo.gl/KwvDNy.
9 | // This link also includes instructions on opting out of this behavior.
10 |
11 | const isLocalhost = Boolean(
12 | window.location.hostname === 'localhost' ||
13 | // [::1] is the IPv6 localhost address.
14 | window.location.hostname === '[::1]' ||
15 | // 127.0.0.1/8 is considered localhost for IPv4.
16 | window.location.hostname.match(
17 | /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
18 | )
19 | );
20 |
21 | export default function register() {
22 | if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
23 | // The URL constructor is available in all browsers that support SW.
24 | const publicUrl = new URL(process.env.PUBLIC_URL, window.location);
25 | if (publicUrl.origin !== window.location.origin) {
26 | // Our service worker won't work if PUBLIC_URL is on a different origin
27 | // from what our page is served on. This might happen if a CDN is used to
28 | // serve assets; see https://github.com/facebookincubator/create-react-app/issues/2374
29 | return;
30 | }
31 |
32 | window.addEventListener('load', () => {
33 | const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
34 |
35 | if (!isLocalhost) {
36 | // Is not local host. Just register service worker
37 | registerValidSW(swUrl);
38 | } else {
39 | // This is running on localhost. Lets check if a service worker still exists or not.
40 | checkValidServiceWorker(swUrl);
41 | }
42 | });
43 | }
44 | }
45 |
46 | function registerValidSW(swUrl) {
47 | navigator.serviceWorker
48 | .register(swUrl)
49 | .then(registration => {
50 | registration.onupdatefound = () => {
51 | const installingWorker = registration.installing;
52 | installingWorker.onstatechange = () => {
53 | if (installingWorker.state === 'installed') {
54 | if (navigator.serviceWorker.controller) {
55 | // At this point, the old content will have been purged and
56 | // the fresh content will have been added to the cache.
57 | // It's the perfect time to display a "New content is
58 | // available; please refresh." message in your web app.
59 | console.log('New content is available; please refresh.');
60 | } else {
61 | // At this point, everything has been precached.
62 | // It's the perfect time to display a
63 | // "Content is cached for offline use." message.
64 | console.log('Content is cached for offline use.');
65 | }
66 | }
67 | };
68 | };
69 | })
70 | .catch(error => {
71 | console.error('Error during service worker registration:', error);
72 | });
73 | }
74 |
75 | function checkValidServiceWorker(swUrl) {
76 | // Check if the service worker can be found. If it can't reload the page.
77 | fetch(swUrl)
78 | .then(response => {
79 | // Ensure service worker exists, and that we really are getting a JS file.
80 | if (
81 | response.status === 404 ||
82 | response.headers.get('content-type').indexOf('javascript') === -1
83 | ) {
84 | // No service worker found. Probably a different app. Reload the page.
85 | navigator.serviceWorker.ready.then(registration => {
86 | registration.unregister().then(() => {
87 | window.location.reload();
88 | });
89 | });
90 | } else {
91 | // Service worker found. Proceed as normal.
92 | registerValidSW(swUrl);
93 | }
94 | })
95 | .catch(() => {
96 | console.log(
97 | 'No internet connection found. App is running in offline mode.'
98 | );
99 | });
100 | }
101 |
102 | export function unregister() {
103 | if ('serviceWorker' in navigator) {
104 | navigator.serviceWorker.ready.then(registration => {
105 | registration.unregister();
106 | });
107 | }
108 | }
109 |
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/client/README.md:
--------------------------------------------------------------------------------
1 | This project was bootstrapped with [Create React App](https://github.com/facebookincubator/create-react-app).
2 |
3 | Below you will find some information on how to perform common tasks.
4 | You can find the most recent version of this guide [here](https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/template/README.md).
5 |
6 | ## Table of Contents
7 |
8 | - [Updating to New Releases](#updating-to-new-releases)
9 | - [Sending Feedback](#sending-feedback)
10 | - [Folder Structure](#folder-structure)
11 | - [Available Scripts](#available-scripts)
12 | - [npm start](#npm-start)
13 | - [npm test](#npm-test)
14 | - [npm run build](#npm-run-build)
15 | - [npm run eject](#npm-run-eject)
16 | - [Supported Language Features and Polyfills](#supported-language-features-and-polyfills)
17 | - [Syntax Highlighting in the Editor](#syntax-highlighting-in-the-editor)
18 | - [Displaying Lint Output in the Editor](#displaying-lint-output-in-the-editor)
19 | - [Debugging in the Editor](#debugging-in-the-editor)
20 | - [Formatting Code Automatically](#formatting-code-automatically)
21 | - [Changing the Page ``](#changing-the-page-title)
22 | - [Installing a Dependency](#installing-a-dependency)
23 | - [Importing a Component](#importing-a-component)
24 | - [Code Splitting](#code-splitting)
25 | - [Adding a Stylesheet](#adding-a-stylesheet)
26 | - [Post-Processing CSS](#post-processing-css)
27 | - [Adding a CSS Preprocessor (Sass, Less etc.)](#adding-a-css-preprocessor-sass-less-etc)
28 | - [Adding Images, Fonts, and Files](#adding-images-fonts-and-files)
29 | - [Using the `public` Folder](#using-the-public-folder)
30 | - [Changing the HTML](#changing-the-html)
31 | - [Adding Assets Outside of the Module System](#adding-assets-outside-of-the-module-system)
32 | - [When to Use the `public` Folder](#when-to-use-the-public-folder)
33 | - [Using Global Variables](#using-global-variables)
34 | - [Adding Bootstrap](#adding-bootstrap)
35 | - [Using a Custom Theme](#using-a-custom-theme)
36 | - [Adding Flow](#adding-flow)
37 | - [Adding Custom Environment Variables](#adding-custom-environment-variables)
38 | - [Referencing Environment Variables in the HTML](#referencing-environment-variables-in-the-html)
39 | - [Adding Temporary Environment Variables In Your Shell](#adding-temporary-environment-variables-in-your-shell)
40 | - [Adding Development Environment Variables In `.env`](#adding-development-environment-variables-in-env)
41 | - [Can I Use Decorators?](#can-i-use-decorators)
42 | - [Integrating with an API Backend](#integrating-with-an-api-backend)
43 | - [Node](#node)
44 | - [Ruby on Rails](#ruby-on-rails)
45 | - [Proxying API Requests in Development](#proxying-api-requests-in-development)
46 | - ["Invalid Host Header" Errors After Configuring Proxy](#invalid-host-header-errors-after-configuring-proxy)
47 | - [Configuring the Proxy Manually](#configuring-the-proxy-manually)
48 | - [Configuring a WebSocket Proxy](#configuring-a-websocket-proxy)
49 | - [Using HTTPS in Development](#using-https-in-development)
50 | - [Generating Dynamic `<meta>` Tags on the Server](#generating-dynamic-meta-tags-on-the-server)
51 | - [Pre-Rendering into Static HTML Files](#pre-rendering-into-static-html-files)
52 | - [Injecting Data from the Server into the Page](#injecting-data-from-the-server-into-the-page)
53 | - [Running Tests](#running-tests)
54 | - [Filename Conventions](#filename-conventions)
55 | - [Command Line Interface](#command-line-interface)
56 | - [Version Control Integration](#version-control-integration)
57 | - [Writing Tests](#writing-tests)
58 | - [Testing Components](#testing-components)
59 | - [Using Third Party Assertion Libraries](#using-third-party-assertion-libraries)
60 | - [Initializing Test Environment](#initializing-test-environment)
61 | - [Focusing and Excluding Tests](#focusing-and-excluding-tests)
62 | - [Coverage Reporting](#coverage-reporting)
63 | - [Continuous Integration](#continuous-integration)
64 | - [Disabling jsdom](#disabling-jsdom)
65 | - [Snapshot Testing](#snapshot-testing)
66 | - [Editor Integration](#editor-integration)
67 | - [Developing Components in Isolation](#developing-components-in-isolation)
68 | - [Getting Started with Storybook](#getting-started-with-storybook)
69 | - [Getting Started with Styleguidist](#getting-started-with-styleguidist)
70 | - [Making a Progressive Web App](#making-a-progressive-web-app)
71 | - [Offline-First Considerations](#offline-first-considerations)
72 | - [Progressive Web App Metadata](#progressive-web-app-metadata)
73 | - [Analyzing the Bundle Size](#analyzing-the-bundle-size)
74 | - [Deployment](#deployment)
75 | - [Static Server](#static-server)
76 | - [Other Solutions](#other-solutions)
77 | - [Serving Apps with Client-Side Routing](#serving-apps-with-client-side-routing)
78 | - [Building for Relative Paths](#building-for-relative-paths)
79 | - [Azure](#azure)
80 | - [Firebase](#firebase)
81 | - [GitHub Pages](#github-pages)
82 | - [Heroku](#heroku)
83 | - [Modulus](#modulus)
84 | - [Netlify](#netlify)
85 | - [Now](#now)
86 | - [S3 and CloudFront](#s3-and-cloudfront)
87 | - [Surge](#surge)
88 | - [Advanced Configuration](#advanced-configuration)
89 | - [Troubleshooting](#troubleshooting)
90 | - [`npm start` doesn’t detect changes](#npm-start-doesnt-detect-changes)
91 | - [`npm test` hangs on macOS Sierra](#npm-test-hangs-on-macos-sierra)
92 | - [`npm run build` exits too early](#npm-run-build-exits-too-early)
93 | - [`npm run build` fails on Heroku](#npm-run-build-fails-on-heroku)
94 | - [Moment.js locales are missing](#momentjs-locales-are-missing)
95 | - [Something Missing?](#something-missing)
96 |
97 | ## Updating to New Releases
98 |
99 | Create React App is divided into two packages:
100 |
101 | * `create-react-app` is a global command-line utility that you use to create new projects.
102 | * `react-scripts` is a development dependency in the generated projects (including this one).
103 |
104 | You almost never need to update `create-react-app` itself: it delegates all the setup to `react-scripts`.
105 |
106 | When you run `create-react-app`, it always creates the project with the latest version of `react-scripts` so you’ll get all the new features and improvements in newly created apps automatically.
107 |
108 | To update an existing project to a new version of `react-scripts`, [open the changelog](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md), find the version you’re currently on (check `package.json` in this folder if you’re not sure), and apply the migration instructions for the newer versions.
109 |
110 | In most cases bumping the `react-scripts` version in `package.json` and running `npm install` in this folder should be enough, but it’s good to consult the [changelog](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md) for potential breaking changes.
111 |
112 | We commit to keeping the breaking changes minimal so you can upgrade `react-scripts` painlessly.
113 |
114 | ## Sending Feedback
115 |
116 | We are always open to [your feedback](https://github.com/facebookincubator/create-react-app/issues).
117 |
118 | ## Folder Structure
119 |
120 | After creation, your project should look like this:
121 |
122 | ```
123 | my-app/
124 | README.md
125 | node_modules/
126 | package.json
127 | public/
128 | index.html
129 | favicon.ico
130 | src/
131 | App.css
132 | App.js
133 | App.test.js
134 | index.css
135 | index.js
136 | logo.svg
137 | ```
138 |
139 | For the project to build, **these files must exist with exact filenames**:
140 |
141 | * `public/index.html` is the page template;
142 | * `src/index.js` is the JavaScript entry point.
143 |
144 | You can delete or rename the other files.
145 |
146 | You may create subdirectories inside `src`. For faster rebuilds, only files inside `src` are processed by Webpack.<br>
147 | You need to **put any JS and CSS files inside `src`**, otherwise Webpack won’t see them.
148 |
149 | Only files inside `public` can be used from `public/index.html`.<br>
150 | Read instructions below for using assets from JavaScript and HTML.
151 |
152 | You can, however, create more top-level directories.<br>
153 | They will not be included in the production build so you can use them for things like documentation.
154 |
155 | ## Available Scripts
156 |
157 | In the project directory, you can run:
158 |
159 | ### `npm start`
160 |
161 | Runs the app in the development mode.<br>
162 | Open [http://localhost:3000](http://localhost:3000) to view it in the browser.
163 |
164 | The page will reload if you make edits.<br>
165 | You will also see any lint errors in the console.
166 |
167 | ### `npm test`
168 |
169 | Launches the test runner in the interactive watch mode.<br>
170 | See the section about [running tests](#running-tests) for more information.
171 |
172 | ### `npm run build`
173 |
174 | Builds the app for production to the `build` folder.<br>
175 | It correctly bundles React in production mode and optimizes the build for the best performance.
176 |
177 | The build is minified and the filenames include the hashes.<br>
178 | Your app is ready to be deployed!
179 |
180 | See the section about [deployment](#deployment) for more information.
181 |
182 | ### `npm run eject`
183 |
184 | **Note: this is a one-way operation. Once you `eject`, you can’t go back!**
185 |
186 | If you aren’t satisfied with the build tool and configuration choices, you can `eject` at any time. This command will remove the single build dependency from your project.
187 |
188 | Instead, it will copy all the configuration files and the transitive dependencies (Webpack, Babel, ESLint, etc) right into your project so you have full control over them. All of the commands except `eject` will still work, but they will point to the copied scripts so you can tweak them. At this point you’re on your own.
189 |
190 | You don’t have to ever use `eject`. The curated feature set is suitable for small and middle deployments, and you shouldn’t feel obligated to use this feature. However we understand that this tool wouldn’t be useful if you couldn’t customize it when you are ready for it.
191 |
192 | ## Supported Language Features and Polyfills
193 |
194 | This project supports a superset of the latest JavaScript standard.<br>
195 | In addition to [ES6](https://github.com/lukehoban/es6features) syntax features, it also supports:
196 |
197 | * [Exponentiation Operator](https://github.com/rwaldron/exponentiation-operator) (ES2016).
198 | * [Async/await](https://github.com/tc39/ecmascript-asyncawait) (ES2017).
199 | * [Object Rest/Spread Properties](https://github.com/sebmarkbage/ecmascript-rest-spread) (stage 3 proposal).
200 | * [Dynamic import()](https://github.com/tc39/proposal-dynamic-import) (stage 3 proposal)
201 | * [Class Fields and Static Properties](https://github.com/tc39/proposal-class-public-fields) (stage 2 proposal).
202 | * [JSX](https://facebook.github.io/react/docs/introducing-jsx.html) and [Flow](https://flowtype.org/) syntax.
203 |
204 | Learn more about [different proposal stages](https://babeljs.io/docs/plugins/#presets-stage-x-experimental-presets-).
205 |
206 | While we recommend to use experimental proposals with some caution, Facebook heavily uses these features in the product code, so we intend to provide [codemods](https://medium.com/@cpojer/effective-javascript-codemods-5a6686bb46fb) if any of these proposals change in the future.
207 |
208 | Note that **the project only includes a few ES6 [polyfills](https://en.wikipedia.org/wiki/Polyfill)**:
209 |
210 | * [`Object.assign()`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/assign) via [`object-assign`](https://github.com/sindresorhus/object-assign).
211 | * [`Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) via [`promise`](https://github.com/then/promise).
212 | * [`fetch()`](https://developer.mozilla.org/en/docs/Web/API/Fetch_API) via [`whatwg-fetch`](https://github.com/github/fetch).
213 |
214 | If you use any other ES6+ features that need **runtime support** (such as `Array.from()` or `Symbol`), make sure you are including the appropriate polyfills manually, or that the browsers you are targeting already support them.
215 |
216 | ## Syntax Highlighting in the Editor
217 |
218 | To configure the syntax highlighting in your favorite text editor, head to the [relevant Babel documentation page](https://babeljs.io/docs/editors) and follow the instructions. Some of the most popular editors are covered.
219 |
220 | ## Displaying Lint Output in the Editor
221 |
222 | >Note: this feature is available with `react-scripts@0.2.0` and higher.<br>
223 | >It also only works with npm 3 or higher.
224 |
225 | Some editors, including Sublime Text, Atom, and Visual Studio Code, provide plugins for ESLint.
226 |
227 | They are not required for linting. You should see the linter output right in your terminal as well as the browser console. However, if you prefer the lint results to appear right in your editor, there are some extra steps you can do.
228 |
229 | You would need to install an ESLint plugin for your editor first. Then, add a file called `.eslintrc` to the project root:
230 |
231 | ```js
232 | {
233 | "extends": "react-app"
234 | }
235 | ```
236 |
237 | Now your editor should report the linting warnings.
238 |
239 | Note that even if you edit your `.eslintrc` file further, these changes will **only affect the editor integration**. They won’t affect the terminal and in-browser lint output. This is because Create React App intentionally provides a minimal set of rules that find common mistakes.
240 |
241 | If you want to enforce a coding style for your project, consider using [Prettier](https://github.com/jlongster/prettier) instead of ESLint style rules.
242 |
243 | ## Debugging in the Editor
244 |
245 | **This feature is currently only supported by [Visual Studio Code](https://code.visualstudio.com) editor.**
246 |
247 | Visual Studio Code supports debugging out of the box with Create React App. This enables you as a developer to write and debug your React code without leaving the editor, and most importantly it enables you to have a continuous development workflow, where context switching is minimal, as you don’t have to switch between tools.
248 |
249 | You would need to have the latest version of [VS Code](https://code.visualstudio.com) and VS Code [Chrome Debugger Extension](https://marketplace.visualstudio.com/items?itemName=msjsdiag.debugger-for-chrome) installed.
250 |
251 | Then add the block below to your `launch.json` file and put it inside the `.vscode` folder in your app’s root directory.
252 |
253 | ```json
254 | {
255 | "version": "0.2.0",
256 | "configurations": [{
257 | "name": "Chrome",
258 | "type": "chrome",
259 | "request": "launch",
260 | "url": "http://localhost:3000",
261 | "webRoot": "${workspaceRoot}/src",
262 | "userDataDir": "${workspaceRoot}/.vscode/chrome",
263 | "sourceMapPathOverrides": {
264 | "webpack:///src/*": "${webRoot}/*"
265 | }
266 | }]
267 | }
268 | ```
269 |
270 | Start your app by running `npm start`, and start debugging in VS Code by pressing `F5` or by clicking the green debug icon. You can now write code, set breakpoints, make changes to the code, and debug your newly modified code—all from your editor.
271 |
272 | ## Formatting Code Automatically
273 |
274 | Prettier is an opinionated code formatter with support for JavaScript, CSS and JSON. With Prettier you can format the code you write automatically to ensure a code style within your project. See the [Prettier's GitHub page](https://github.com/prettier/prettier) for more information, and look at this [page to see it in action](https://prettier.github.io/prettier/).
275 |
276 | To format our code whenever we make a commit in git, we need to install the following dependencies:
277 |
278 | ```sh
279 | npm install --save husky lint-staged prettier
280 | ```
281 |
282 | Alternatively you may use `yarn`:
283 |
284 | ```sh
285 | yarn add husky lint-staged prettier
286 | ```
287 |
288 | * `husky` makes it easy to use githooks as if they are npm scripts.
289 | * `lint-staged` allows us to run scripts on staged files in git. See this [blog post about lint-staged to learn more about it](https://medium.com/@okonetchnikov/make-linting-great-again-f3890e1ad6b8).
290 | * `prettier` is the JavaScript formatter we will run before commits.
291 |
292 | Now we can make sure every file is formatted correctly by adding a few lines to the `package.json` in the project root.
293 |
294 | Add the following line to `scripts` section:
295 |
296 | ```diff
297 | "scripts": {
298 | + "precommit": "lint-staged",
299 | "start": "react-scripts start",
300 | "build": "react-scripts build",
301 | ```
302 |
303 | Next we add a 'lint-staged' field to the `package.json`, for example:
304 |
305 | ```diff
306 | "dependencies": {
307 | // ...
308 | },
309 | + "lint-staged": {
310 | + "src/**/*.{js,jsx,json,css}": [
311 | + "prettier --single-quote --write",
312 | + "git add"
313 | + ]
314 | + },
315 | "scripts": {
316 | ```
317 |
318 | Now, whenever you make a commit, Prettier will format the changed files automatically. You can also run `./node_modules/.bin/prettier --single-quote --write "src/**/*.{js,jsx}"` to format your entire project for the first time.
319 |
320 | Next you might want to integrate Prettier in your favorite editor. Read the section on [Editor Integration](https://github.com/prettier/prettier#editor-integration) on the Prettier GitHub page.
321 |
322 | ## Changing the Page `<title>`
323 |
324 | You can find the source HTML file in the `public` folder of the generated project. You may edit the `<title>` tag in it to change the title from “React App” to anything else.
325 |
326 | Note that normally you wouldn’t edit files in the `public` folder very often. For example, [adding a stylesheet](#adding-a-stylesheet) is done without touching the HTML.
327 |
328 | If you need to dynamically update the page title based on the content, you can use the browser [`document.title`](https://developer.mozilla.org/en-US/docs/Web/API/Document/title) API. For more complex scenarios when you want to change the title from React components, you can use [React Helmet](https://github.com/nfl/react-helmet), a third party library.
329 |
330 | If you use a custom server for your app in production and want to modify the title before it gets sent to the browser, you can follow advice in [this section](#generating-dynamic-meta-tags-on-the-server). Alternatively, you can pre-build each page as a static HTML file which then loads the JavaScript bundle, which is covered [here](#pre-rendering-into-static-html-files).
331 |
332 | ## Installing a Dependency
333 |
334 | The generated project includes React and ReactDOM as dependencies. It also includes a set of scripts used by Create React App as a development dependency. You may install other dependencies (for example, React Router) with `npm`:
335 |
336 | ```sh
337 | npm install --save react-router
338 | ```
339 |
340 | Alternatively you may use `yarn`:
341 |
342 | ```sh
343 | yarn add react-router
344 | ```
345 |
346 | This works for any library, not just `react-router`.
347 |
348 | ## Importing a Component
349 |
350 | This project setup supports ES6 modules thanks to Babel.<br>
351 | While you can still use `require()` and `module.exports`, we encourage you to use [`import` and `export`](http://exploringjs.com/es6/ch_modules.html) instead.
352 |
353 | For example:
354 |
355 | ### `Button.js`
356 |
357 | ```js
358 | import React, { Component } from 'react';
359 |
360 | class Button extends Component {
361 | render() {
362 | // ...
363 | }
364 | }
365 |
366 | export default Button; // Don’t forget to use export default!
367 | ```
368 |
369 | ### `DangerButton.js`
370 |
371 |
372 | ```js
373 | import React, { Component } from 'react';
374 | import Button from './Button'; // Import a component from another file
375 |
376 | class DangerButton extends Component {
377 | render() {
378 | return <Button color="red" />;
379 | }
380 | }
381 |
382 | export default DangerButton;
383 | ```
384 |
385 | Be aware of the [difference between default and named exports](http://stackoverflow.com/questions/36795819/react-native-es-6-when-should-i-use-curly-braces-for-import/36796281#36796281). It is a common source of mistakes.
386 |
387 | We suggest that you stick to using default imports and exports when a module only exports a single thing (for example, a component). That’s what you get when you use `export default Button` and `import Button from './Button'`.
388 |
389 | Named exports are useful for utility modules that export several functions. A module may have at most one default export and as many named exports as you like.
390 |
391 | Learn more about ES6 modules:
392 |
393 | * [When to use the curly braces?](http://stackoverflow.com/questions/36795819/react-native-es-6-when-should-i-use-curly-braces-for-import/36796281#36796281)
394 | * [Exploring ES6: Modules](http://exploringjs.com/es6/ch_modules.html)
395 | * [Understanding ES6: Modules](https://leanpub.com/understandinges6/read#leanpub-auto-encapsulating-code-with-modules)
396 |
397 | ## Code Splitting
398 |
399 | Instead of downloading the entire app before users can use it, code splitting allows you to split your code into small chunks which you can then load on demand.
400 |
401 | This project setup supports code splitting via [dynamic `import()`](http://2ality.com/2017/01/import-operator.html#loading-code-on-demand). Its [proposal](https://github.com/tc39/proposal-dynamic-import) is in stage 3. The `import()` function-like form takes the module name as an argument and returns a [`Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) which always resolves to the namespace object of the module.
402 |
403 | Here is an example:
404 |
405 | ### `moduleA.js`
406 |
407 | ```js
408 | const moduleA = 'Hello';
409 |
410 | export { moduleA };
411 | ```
412 | ### `App.js`
413 |
414 | ```js
415 | import React, { Component } from 'react';
416 |
417 | class App extends Component {
418 | handleClick = () => {
419 | import('./moduleA')
420 | .then(({ moduleA }) => {
421 | // Use moduleA
422 | })
423 | .catch(err => {
424 | // Handle failure
425 | });
426 | };
427 |
428 | render() {
429 | return (
430 | <div>
431 | <button onClick={this.handleClick}>Load</button>
432 | </div>
433 | );
434 | }
435 | }
436 |
437 | export default App;
438 | ```
439 |
440 | This will make `moduleA.js` and all its unique dependencies as a separate chunk that only loads after the user clicks the 'Load' button.
441 |
442 | You can also use it with `async` / `await` syntax if you prefer it.
443 |
444 | ### With React Router
445 |
446 | If you are using React Router check out [this tutorial](http://serverless-stack.com/chapters/code-splitting-in-create-react-app.html) on how to use code splitting with it. You can find the companion GitHub repository [here](https://github.com/AnomalyInnovations/serverless-stack-demo-client/tree/code-splitting-in-create-react-app).
447 |
448 | ## Adding a Stylesheet
449 |
450 | This project setup uses [Webpack](https://webpack.js.org/) for handling all assets. Webpack offers a custom way of “extending” the concept of `import` beyond JavaScript. To express that a JavaScript file depends on a CSS file, you need to **import the CSS from the JavaScript file**:
451 |
452 | ### `Button.css`
453 |
454 | ```css
455 | .Button {
456 | padding: 20px;
457 | }
458 | ```
459 |
460 | ### `Button.js`
461 |
462 | ```js
463 | import React, { Component } from 'react';
464 | import './Button.css'; // Tell Webpack that Button.js uses these styles
465 |
466 | class Button extends Component {
467 | render() {
468 | // You can use them as regular CSS styles
469 | return <div className="Button" />;
470 | }
471 | }
472 | ```
473 |
474 | **This is not required for React** but many people find this feature convenient. You can read about the benefits of this approach [here](https://medium.com/seek-ui-engineering/block-element-modifying-your-javascript-components-d7f99fcab52b). However you should be aware that this makes your code less portable to other build tools and environments than Webpack.
475 |
476 | In development, expressing dependencies this way allows your styles to be reloaded on the fly as you edit them. In production, all CSS files will be concatenated into a single minified `.css` file in the build output.
477 |
478 | If you are concerned about using Webpack-specific semantics, you can put all your CSS right into `src/index.css`. It would still be imported from `src/index.js`, but you could always remove that import if you later migrate to a different build tool.
479 |
480 | ## Post-Processing CSS
481 |
482 | This project setup minifies your CSS and adds vendor prefixes to it automatically through [Autoprefixer](https://github.com/postcss/autoprefixer) so you don’t need to worry about it.
483 |
484 | For example, this:
485 |
486 | ```css
487 | .App {
488 | display: flex;
489 | flex-direction: row;
490 | align-items: center;
491 | }
492 | ```
493 |
494 | becomes this:
495 |
496 | ```css
497 | .App {
498 | display: -webkit-box;
499 | display: -ms-flexbox;
500 | display: flex;
501 | -webkit-box-orient: horizontal;
502 | -webkit-box-direction: normal;
503 | -ms-flex-direction: row;
504 | flex-direction: row;
505 | -webkit-box-align: center;
506 | -ms-flex-align: center;
507 | align-items: center;
508 | }
509 | ```
510 |
511 | If you need to disable autoprefixing for some reason, [follow this section](https://github.com/postcss/autoprefixer#disabling).
512 |
513 | ## Adding a CSS Preprocessor (Sass, Less etc.)
514 |
515 | Generally, we recommend that you don’t reuse the same CSS classes across different components. For example, instead of using a `.Button` CSS class in `<AcceptButton>` and `<RejectButton>` components, we recommend creating a `<Button>` component with its own `.Button` styles, that both `<AcceptButton>` and `<RejectButton>` can render (but [not inherit](https://facebook.github.io/react/docs/composition-vs-inheritance.html)).
516 |
517 | Following this rule often makes CSS preprocessors less useful, as features like mixins and nesting are replaced by component composition. You can, however, integrate a CSS preprocessor if you find it valuable. In this walkthrough, we will be using Sass, but you can also use Less, or another alternative.
518 |
519 | First, let’s install the command-line interface for Sass:
520 |
521 | ```sh
522 | npm install --save node-sass-chokidar
523 | ```
524 |
525 | Alternatively you may use `yarn`:
526 |
527 | ```sh
528 | yarn add node-sass-chokidar
529 | ```
530 |
531 | Then in `package.json`, add the following lines to `scripts`:
532 |
533 | ```diff
534 | "scripts": {
535 | + "build-css": "node-sass-chokidar src/ -o src/",
536 | + "watch-css": "npm run build-css && node-sass-chokidar src/ -o src/ --watch --recursive",
537 | "start": "react-scripts start",
538 | "build": "react-scripts build",
539 | "test": "react-scripts test --env=jsdom",
540 | ```
541 |
542 | >Note: To use a different preprocessor, replace `build-css` and `watch-css` commands according to your preprocessor’s documentation.
543 |
544 | Now you can rename `src/App.css` to `src/App.scss` and run `npm run watch-css`. The watcher will find every Sass file in `src` subdirectories, and create a corresponding CSS file next to it, in our case overwriting `src/App.css`. Since `src/App.js` still imports `src/App.css`, the styles become a part of your application. You can now edit `src/App.scss`, and `src/App.css` will be regenerated.
545 |
546 | To share variables between Sass files, you can use Sass imports. For example, `src/App.scss` and other component style files could include `@import "./shared.scss";` with variable definitions.
547 |
548 | To enable importing files without using relative paths, you can add the `--include-path` option to the command in `package.json`.
549 |
550 | ```
551 | "build-css": "node-sass-chokidar --include-path ./src --include-path ./node_modules src/ -o src/",
552 | "watch-css": "npm run build-css && node-sass-chokidar --include-path ./src --include-path ./node_modules src/ -o src/ --watch --recursive",
553 | ```
554 |
555 | This will allow you to do imports like
556 |
557 | ```scss
558 | @import 'styles/_colors.scss'; // assuming a styles directory under src/
559 | @import 'nprogress/nprogress'; // importing a css file from the nprogress node module
560 | ```
561 |
562 | At this point you might want to remove all CSS files from the source control, and add `src/**/*.css` to your `.gitignore` file. It is generally a good practice to keep the build products outside of the source control.
563 |
564 | As a final step, you may find it convenient to run `watch-css` automatically with `npm start`, and run `build-css` as a part of `npm run build`. You can use the `&&` operator to execute two scripts sequentially. However, there is no cross-platform way to run two scripts in parallel, so we will install a package for this:
565 |
566 | ```sh
567 | npm install --save npm-run-all
568 | ```
569 |
570 | Alternatively you may use `yarn`:
571 |
572 | ```sh
573 | yarn add npm-run-all
574 | ```
575 |
576 | Then we can change `start` and `build` scripts to include the CSS preprocessor commands:
577 |
578 | ```diff
579 | "scripts": {
580 | "build-css": "node-sass-chokidar src/ -o src/",
581 | "watch-css": "npm run build-css && node-sass-chokidar src/ -o src/ --watch --recursive",
582 | - "start": "react-scripts start",
583 | - "build": "react-scripts build",
584 | + "start-js": "react-scripts start",
585 | + "start": "npm-run-all -p watch-css start-js",
586 | + "build": "npm run build-css && react-scripts build",
587 | "test": "react-scripts test --env=jsdom",
588 | "eject": "react-scripts eject"
589 | }
590 | ```
591 |
592 | Now running `npm start` and `npm run build` also builds Sass files.
593 |
594 | **Why `node-sass-chokidar`?**
595 |
596 | `node-sass` has been reported as having the following issues:
597 |
598 | - `node-sass --watch` has been reported to have *performance issues* in certain conditions when used in a virtual machine or with docker.
599 |
600 | - Infinite styles compiling [#1939](https://github.com/facebookincubator/create-react-app/issues/1939)
601 |
602 | - `node-sass` has been reported as having issues with detecting new files in a directory [#1891](https://github.com/sass/node-sass/issues/1891)
603 |
604 | `node-sass-chokidar` is used here as it addresses these issues.
605 |
606 | ## Adding Images, Fonts, and Files
607 |
608 | With Webpack, using static assets like images and fonts works similarly to CSS.
609 |
610 | You can **`import` a file right in a JavaScript module**. This tells Webpack to include that file in the bundle. Unlike CSS imports, importing a file gives you a string value. This value is the final path you can reference in your code, e.g. as the `src` attribute of an image or the `href` of a link to a PDF.
611 |
612 | To reduce the number of requests to the server, importing images that are less than 10,000 bytes returns a [data URI](https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/Data_URIs) instead of a path. This applies to the following file extensions: bmp, gif, jpg, jpeg, and png. SVG files are excluded due to [#1153](https://github.com/facebookincubator/create-react-app/issues/1153).
613 |
614 | Here is an example:
615 |
616 | ```js
617 | import React from 'react';
618 | import logo from './logo.png'; // Tell Webpack this JS file uses this image
619 |
620 | console.log(logo); // /logo.84287d09.png
621 |
622 | function Header() {
623 | // Import result is the URL of your image
624 | return <img src={logo} alt="Logo" />;
625 | }
626 |
627 | export default Header;
628 | ```
629 |
630 | This ensures that when the project is built, Webpack will correctly move the images into the build folder, and provide us with correct paths.
631 |
632 | This works in CSS too:
633 |
634 | ```css
635 | .Logo {
636 | background-image: url(./logo.png);
637 | }
638 | ```
639 |
640 | Webpack finds all relative module references in CSS (they start with `./`) and replaces them with the final paths from the compiled bundle. If you make a typo or accidentally delete an important file, you will see a compilation error, just like when you import a non-existent JavaScript module. The final filenames in the compiled bundle are generated by Webpack from content hashes. If the file content changes in the future, Webpack will give it a different name in production so you don’t need to worry about long-term caching of assets.
641 |
642 | Please be advised that this is also a custom feature of Webpack.
643 |
644 | **It is not required for React** but many people enjoy it (and React Native uses a similar mechanism for images).<br>
645 | An alternative way of handling static assets is described in the next section.
646 |
647 | ## Using the `public` Folder
648 |
649 | >Note: this feature is available with `react-scripts@0.5.0` and higher.
650 |
651 | ### Changing the HTML
652 |
653 | The `public` folder contains the HTML file so you can tweak it, for example, to [set the page title](#changing-the-page-title).
654 | The `<script>` tag with the compiled code will be added to it automatically during the build process.
655 |
656 | ### Adding Assets Outside of the Module System
657 |
658 | You can also add other assets to the `public` folder.
659 |
660 | Note that we normally encourage you to `import` assets in JavaScript files instead.
661 | For example, see the sections on [adding a stylesheet](#adding-a-stylesheet) and [adding images and fonts](#adding-images-fonts-and-files).
662 | This mechanism provides a number of benefits:
663 |
664 | * Scripts and stylesheets get minified and bundled together to avoid extra network requests.
665 | * Missing files cause compilation errors instead of 404 errors for your users.
666 | * Result filenames include content hashes so you don’t need to worry about browsers caching their old versions.
667 |
668 | However there is an **escape hatch** that you can use to add an asset outside of the module system.
669 |
670 | If you put a file into the `public` folder, it will **not** be processed by Webpack. Instead it will be copied into the build folder untouched. To reference assets in the `public` folder, you need to use a special variable called `PUBLIC_URL`.
671 |
672 | Inside `index.html`, you can use it like this:
673 |
674 | ```html
675 | <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
676 | ```
677 |
678 | Only files inside the `public` folder will be accessible by `%PUBLIC_URL%` prefix. If you need to use a file from `src` or `node_modules`, you’ll have to copy it there to explicitly specify your intention to make this file a part of the build.
679 |
680 | When you run `npm run build`, Create React App will substitute `%PUBLIC_URL%` with a correct absolute path so your project works even if you use client-side routing or host it at a non-root URL.
681 |
682 | In JavaScript code, you can use `process.env.PUBLIC_URL` for similar purposes:
683 |
684 | ```js
685 | render() {
686 | // Note: this is an escape hatch and should be used sparingly!
687 | // Normally we recommend using `import` for getting asset URLs
688 | // as described in “Adding Images and Fonts” above this section.
689 | return <img src={process.env.PUBLIC_URL + '/img/logo.png'} />;
690 | }
691 | ```
692 |
693 | Keep in mind the downsides of this approach:
694 |
695 | * None of the files in `public` folder get post-processed or minified.
696 | * Missing files will not be called at compilation time, and will cause 404 errors for your users.
697 | * Result filenames won’t include content hashes so you’ll need to add query arguments or rename them every time they change.
698 |
699 | ### When to Use the `public` Folder
700 |
701 | Normally we recommend importing [stylesheets](#adding-a-stylesheet), [images, and fonts](#adding-images-fonts-and-files) from JavaScript.
702 | The `public` folder is useful as a workaround for a number of less common cases:
703 |
704 | * You need a file with a specific name in the build output, such as [`manifest.webmanifest`](https://developer.mozilla.org/en-US/docs/Web/Manifest).
705 | * You have thousands of images and need to dynamically reference their paths.
706 | * You want to include a small script like [`pace.js`](http://github.hubspot.com/pace/docs/welcome/) outside of the bundled code.
707 | * Some library may be incompatible with Webpack and you have no other option but to include it as a `<script>` tag.
708 |
709 | Note that if you add a `<script>` that declares global variables, you also need to read the next section on using them.
710 |
711 | ## Using Global Variables
712 |
713 | When you include a script in the HTML file that defines global variables and try to use one of these variables in the code, the linter will complain because it cannot see the definition of the variable.
714 |
715 | You can avoid this by reading the global variable explicitly from the `window` object, for example:
716 |
717 | ```js
718 | const $ = window.$;
719 | ```
720 |
721 | This makes it obvious you are using a global variable intentionally rather than because of a typo.
722 |
723 | Alternatively, you can force the linter to ignore any line by adding `// eslint-disable-line` after it.
724 |
725 | ## Adding Bootstrap
726 |
727 | You don’t have to use [React Bootstrap](https://react-bootstrap.github.io) together with React but it is a popular library for integrating Bootstrap with React apps. If you need it, you can integrate it with Create React App by following these steps:
728 |
729 | Install React Bootstrap and Bootstrap from npm. React Bootstrap does not include Bootstrap CSS so this needs to be installed as well:
730 |
731 | ```sh
732 | npm install --save react-bootstrap bootstrap@3
733 | ```
734 |
735 | Alternatively you may use `yarn`:
736 |
737 | ```sh
738 | yarn add react-bootstrap bootstrap@3
739 | ```
740 |
741 | Import Bootstrap CSS and optionally Bootstrap theme CSS in the beginning of your ```src/index.js``` file:
742 |
743 | ```js
744 | import 'bootstrap/dist/css/bootstrap.css';
745 | import 'bootstrap/dist/css/bootstrap-theme.css';
746 | // Put any other imports below so that CSS from your
747 | // components takes precedence over default styles.
748 | ```
749 |
750 | Import required React Bootstrap components within ```src/App.js``` file or your custom component files:
751 |
752 | ```js
753 | import { Navbar, Jumbotron, Button } from 'react-bootstrap';
754 | ```
755 |
756 | Now you are ready to use the imported React Bootstrap components within your component hierarchy defined in the render method. Here is an example [`App.js`](https://gist.githubusercontent.com/gaearon/85d8c067f6af1e56277c82d19fd4da7b/raw/6158dd991b67284e9fc8d70b9d973efe87659d72/App.js) redone using React Bootstrap.
757 |
758 | ### Using a Custom Theme
759 |
760 | Sometimes you might need to tweak the visual styles of Bootstrap (or equivalent package).<br>
761 | We suggest the following approach:
762 |
763 | * Create a new package that depends on the package you wish to customize, e.g. Bootstrap.
764 | * Add the necessary build steps to tweak the theme, and publish your package on npm.
765 | * Install your own theme npm package as a dependency of your app.
766 |
767 | Here is an example of adding a [customized Bootstrap](https://medium.com/@tacomanator/customizing-create-react-app-aa9ffb88165) that follows these steps.
768 |
769 | ## Adding Flow
770 |
771 | Flow is a static type checker that helps you write code with fewer bugs. Check out this [introduction to using static types in JavaScript](https://medium.com/@preethikasireddy/why-use-static-types-in-javascript-part-1-8382da1e0adb) if you are new to this concept.
772 |
773 | Recent versions of [Flow](http://flowtype.org/) work with Create React App projects out of the box.
774 |
775 | To add Flow to a Create React App project, follow these steps:
776 |
777 | 1. Run `npm install --save flow-bin` (or `yarn add flow-bin`).
778 | 2. Add `"flow": "flow"` to the `scripts` section of your `package.json`.
779 | 3. Run `npm run flow init` (or `yarn flow init`) to create a [`.flowconfig` file](https://flowtype.org/docs/advanced-configuration.html) in the root directory.
780 | 4. Add `// @flow` to any files you want to type check (for example, to `src/App.js`).
781 |
782 | Now you can run `npm run flow` (or `yarn flow`) to check the files for type errors.
783 | You can optionally use an IDE like [Nuclide](https://nuclide.io/docs/languages/flow/) for a better integrated experience.
784 | In the future we plan to integrate it into Create React App even more closely.
785 |
786 | To learn more about Flow, check out [its documentation](https://flowtype.org/).
787 |
788 | ## Adding Custom Environment Variables
789 |
790 | >Note: this feature is available with `react-scripts@0.2.3` and higher.
791 |
792 | Your project can consume variables declared in your environment as if they were declared locally in your JS files. By
793 | default you will have `NODE_ENV` defined for you, and any other environment variables starting with
794 | `REACT_APP_`.
795 |
796 | **The environment variables are embedded during the build time**. Since Create React App produces a static HTML/CSS/JS bundle, it can’t possibly read them at runtime. To read them at runtime, you would need to load HTML into memory on the server and replace placeholders in runtime, just like [described here](#injecting-data-from-the-server-into-the-page). Alternatively you can rebuild the app on the server anytime you change them.
797 |
798 | >Note: You must create custom environment variables beginning with `REACT_APP_`. Any other variables except `NODE_ENV` will be ignored to avoid accidentally [exposing a private key on the machine that could have the same name](https://github.com/facebookincubator/create-react-app/issues/865#issuecomment-252199527). Changing any environment variables will require you to restart the development server if it is running.
799 |
800 | These environment variables will be defined for you on `process.env`. For example, having an environment
801 | variable named `REACT_APP_SECRET_CODE` will be exposed in your JS as `process.env.REACT_APP_SECRET_CODE`.
802 |
803 | There is also a special built-in environment variable called `NODE_ENV`. You can read it from `process.env.NODE_ENV`. When you run `npm start`, it is always equal to `'development'`, when you run `npm test` it is always equal to `'test'`, and when you run `npm run build` to make a production bundle, it is always equal to `'production'`. **You cannot override `NODE_ENV` manually.** This prevents developers from accidentally deploying a slow development build to production.
804 |
805 | These environment variables can be useful for displaying information conditionally based on where the project is
806 | deployed or consuming sensitive data that lives outside of version control.
807 |
808 | First, you need to have environment variables defined. For example, let’s say you wanted to consume a secret defined
809 | in the environment inside a `<form>`:
810 |
811 | ```jsx
812 | render() {
813 | return (
814 | <div>
815 | <small>You are running this application in <b>{process.env.NODE_ENV}</b> mode.</small>
816 | <form>
817 | <input type="hidden" defaultValue={process.env.REACT_APP_SECRET_CODE} />
818 | </form>
819 | </div>
820 | );
821 | }
822 | ```
823 |
824 | During the build, `process.env.REACT_APP_SECRET_CODE` will be replaced with the current value of the `REACT_APP_SECRET_CODE` environment variable. Remember that the `NODE_ENV` variable will be set for you automatically.
825 |
826 | When you load the app in the browser and inspect the `<input>`, you will see its value set to `abcdef`, and the bold text will show the environment provided when using `npm start`:
827 |
828 | ```html
829 | <div>
830 | <small>You are running this application in <b>development</b> mode.</small>
831 | <form>
832 | <input type="hidden" value="abcdef" />
833 | </form>
834 | </div>
835 | ```
836 |
837 | The above form is looking for a variable called `REACT_APP_SECRET_CODE` from the environment. In order to consume this
838 | value, we need to have it defined in the environment. This can be done using two ways: either in your shell or in
839 | a `.env` file. Both of these ways are described in the next few sections.
840 |
841 | Having access to the `NODE_ENV` is also useful for performing actions conditionally:
842 |
843 | ```js
844 | if (process.env.NODE_ENV !== 'production') {
845 | analytics.disable();
846 | }
847 | ```
848 |
849 | When you compile the app with `npm run build`, the minification step will strip out this condition, and the resulting bundle will be smaller.
850 |
851 | ### Referencing Environment Variables in the HTML
852 |
853 | >Note: this feature is available with `react-scripts@0.9.0` and higher.
854 |
855 | You can also access the environment variables starting with `REACT_APP_` in the `public/index.html`. For example:
856 |
857 | ```html
858 | <title>%REACT_APP_WEBSITE_NAME%
859 | ```
860 |
861 | Note that the caveats from the above section apply:
862 |
863 | * Apart from a few built-in variables (`NODE_ENV` and `PUBLIC_URL`), variable names must start with `REACT_APP_` to work.
864 | * The environment variables are injected at build time. If you need to inject them at runtime, [follow this approach instead](#generating-dynamic-meta-tags-on-the-server).
865 |
866 | ### Adding Temporary Environment Variables In Your Shell
867 |
868 | Defining environment variables can vary between OSes. It’s also important to know that this manner is temporary for the
869 | life of the shell session.
870 |
871 | #### Windows (cmd.exe)
872 |
873 | ```cmd
874 | set REACT_APP_SECRET_CODE=abcdef&&npm start
875 | ```
876 |
877 | (Note: the lack of whitespace is intentional.)
878 |
879 | #### Linux, macOS (Bash)
880 |
881 | ```bash
882 | REACT_APP_SECRET_CODE=abcdef npm start
883 | ```
884 |
885 | ### Adding Development Environment Variables In `.env`
886 |
887 | >Note: this feature is available with `react-scripts@0.5.0` and higher.
888 |
889 | To define permanent environment variables, create a file called `.env` in the root of your project:
890 |
891 | ```
892 | REACT_APP_SECRET_CODE=abcdef
893 | ```
894 |
895 | `.env` files **should be** checked into source control (with the exclusion of `.env*.local`).
896 |
897 | #### What other `.env` files are can be used?
898 |
899 | >Note: this feature is **available with `react-scripts@1.0.0` and higher**.
900 |
901 | * `.env`: Default.
902 | * `.env.local`: Local overrides. **This file is loaded for all environments except test.**
903 | * `.env.development`, `.env.test`, `.env.production`: Environment-specific settings.
904 | * `.env.development.local`, `.env.test.local`, `.env.production.local`: Local overrides of environment-specific settings.
905 |
906 | Files on the left have more priority than files on the right:
907 |
908 | * `npm start`: `.env.development.local`, `.env.development`, `.env.local`, `.env`
909 | * `npm run build`: `.env.production.local`, `.env.production`, `.env.local`, `.env`
910 | * `npm test`: `.env.test.local`, `.env.test`, `.env` (note `.env.local` is missing)
911 |
912 | These variables will act as the defaults if the machine does not explicitly set them.
913 | Please refer to the [dotenv documentation](https://github.com/motdotla/dotenv) for more details.
914 |
915 | >Note: If you are defining environment variables for development, your CI and/or hosting platform will most likely need
916 | these defined as well. Consult their documentation how to do this. For example, see the documentation for [Travis CI](https://docs.travis-ci.com/user/environment-variables/) or [Heroku](https://devcenter.heroku.com/articles/config-vars).
917 |
918 | ## Can I Use Decorators?
919 |
920 | Many popular libraries use [decorators](https://medium.com/google-developers/exploring-es7-decorators-76ecb65fb841) in their documentation.
921 | Create React App doesn’t support decorator syntax at the moment because:
922 |
923 | * It is an experimental proposal and is subject to change.
924 | * The current specification version is not officially supported by Babel.
925 | * If the specification changes, we won’t be able to write a codemod because we don’t use them internally at Facebook.
926 |
927 | However in many cases you can rewrite decorator-based code without decorators just as fine.
928 | Please refer to these two threads for reference:
929 |
930 | * [#214](https://github.com/facebookincubator/create-react-app/issues/214)
931 | * [#411](https://github.com/facebookincubator/create-react-app/issues/411)
932 |
933 | Create React App will add decorator support when the specification advances to a stable stage.
934 |
935 | ## Integrating with an API Backend
936 |
937 | These tutorials will help you to integrate your app with an API backend running on another port,
938 | using `fetch()` to access it.
939 |
940 | ### Node
941 | Check out [this tutorial](https://www.fullstackreact.com/articles/using-create-react-app-with-a-server/).
942 | You can find the companion GitHub repository [here](https://github.com/fullstackreact/food-lookup-demo).
943 |
944 | ### Ruby on Rails
945 |
946 | Check out [this tutorial](https://www.fullstackreact.com/articles/how-to-get-create-react-app-to-work-with-your-rails-api/).
947 | You can find the companion GitHub repository [here](https://github.com/fullstackreact/food-lookup-demo-rails).
948 |
949 | ## Proxying API Requests in Development
950 |
951 | >Note: this feature is available with `react-scripts@0.2.3` and higher.
952 |
953 | People often serve the front-end React app from the same host and port as their backend implementation.
954 | For example, a production setup might look like this after the app is deployed:
955 |
956 | ```
957 | / - static server returns index.html with React app
958 | /todos - static server returns index.html with React app
959 | /api/todos - server handles any /api/* requests using the backend implementation
960 | ```
961 |
962 | Such setup is **not** required. However, if you **do** have a setup like this, it is convenient to write requests like `fetch('/api/todos')` without worrying about redirecting them to another host or port during development.
963 |
964 | To tell the development server to proxy any unknown requests to your API server in development, add a `proxy` field to your `package.json`, for example:
965 |
966 | ```js
967 | "proxy": "http://localhost:4000",
968 | ```
969 |
970 | This way, when you `fetch('/api/todos')` in development, the development server will recognize that it’s not a static asset, and will proxy your request to `http://localhost:4000/api/todos` as a fallback. The development server will only attempt to send requests without a `text/html` accept header to the proxy.
971 |
972 | Conveniently, this avoids [CORS issues](http://stackoverflow.com/questions/21854516/understanding-ajax-cors-and-security-considerations) and error messages like this in development:
973 |
974 | ```
975 | Fetch API cannot load http://localhost:4000/api/todos. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
976 | ```
977 |
978 | Keep in mind that `proxy` only has effect in development (with `npm start`), and it is up to you to ensure that URLs like `/api/todos` point to the right thing in production. You don’t have to use the `/api` prefix. Any unrecognized request without a `text/html` accept header will be redirected to the specified `proxy`.
979 |
980 | The `proxy` option supports HTTP, HTTPS and WebSocket connections.
981 | If the `proxy` option is **not** flexible enough for you, alternatively you can:
982 |
983 | * [Configure the proxy yourself](#configuring-the-proxy-manually)
984 | * Enable CORS on your server ([here’s how to do it for Express](http://enable-cors.org/server_expressjs.html)).
985 | * Use [environment variables](#adding-custom-environment-variables) to inject the right server host and port into your app.
986 |
987 | ### "Invalid Host Header" Errors After Configuring Proxy
988 |
989 | When you enable the `proxy` option, you opt into a more strict set of host checks. This is necessary because leaving the backend open to remote hosts makes your computer vulnerable to DNS rebinding attacks. The issue is explained in [this article](https://medium.com/webpack/webpack-dev-server-middleware-security-issues-1489d950874a) and [this issue](https://github.com/webpack/webpack-dev-server/issues/887).
990 |
991 | This shouldn’t affect you when developing on `localhost`, but if you develop remotely like [described here](https://github.com/facebookincubator/create-react-app/issues/2271), you will see this error in the browser after enabling the `proxy` option:
992 |
993 | >Invalid Host header
994 |
995 | To work around it, you can specify your public development host in a file called `.env.development` in the root of your project:
996 |
997 | ```
998 | HOST=mypublicdevhost.com
999 | ```
1000 |
1001 | If you restart the development server now and load the app from the specified host, it should work.
1002 |
1003 | If you are still having issues or if you’re using a more exotic environment like a cloud editor, you can bypass the host check completely by adding a line to `.env.development.local`. **Note that this is dangerous and exposes your machine to remote code execution from malicious websites:**
1004 |
1005 | ```
1006 | # NOTE: THIS IS DANGEROUS!
1007 | # It exposes your machine to attacks from the websites you visit.
1008 | DANGEROUSLY_DISABLE_HOST_CHECK=true
1009 | ```
1010 |
1011 | We don’t recommend this approach.
1012 |
1013 | ### Configuring the Proxy Manually
1014 |
1015 | >Note: this feature is available with `react-scripts@1.0.0` and higher.
1016 |
1017 | If the `proxy` option is **not** flexible enough for you, you can specify an object in the following form (in `package.json`).
1018 | You may also specify any configuration value [`http-proxy-middleware`](https://github.com/chimurai/http-proxy-middleware#options) or [`http-proxy`](https://github.com/nodejitsu/node-http-proxy#options) supports.
1019 | ```js
1020 | {
1021 | // ...
1022 | "proxy": {
1023 | "/api": {
1024 | "target": "",
1025 | "ws": true
1026 | // ...
1027 | }
1028 | }
1029 | // ...
1030 | }
1031 | ```
1032 |
1033 | All requests matching this path will be proxies, no exceptions. This includes requests for `text/html`, which the standard `proxy` option does not proxy.
1034 |
1035 | If you need to specify multiple proxies, you may do so by specifying additional entries.
1036 | You may also narrow down matches using `*` and/or `**`, to match the path exactly or any subpath.
1037 | ```js
1038 | {
1039 | // ...
1040 | "proxy": {
1041 | // Matches any request starting with /api
1042 | "/api": {
1043 | "target": "",
1044 | "ws": true
1045 | // ...
1046 | },
1047 | // Matches any request starting with /foo
1048 | "/foo": {
1049 | "target": "",
1050 | "ssl": true,
1051 | "pathRewrite": {
1052 | "^/foo": "/foo/beta"
1053 | }
1054 | // ...
1055 | },
1056 | // Matches /bar/abc.html but not /bar/sub/def.html
1057 | "/bar/*.html": {
1058 | "target": "",
1059 | // ...
1060 | },
1061 | // Matches /baz/abc.html and /baz/sub/def.html
1062 | "/baz/**/*.html": {
1063 | "target": ""
1064 | // ...
1065 | }
1066 | }
1067 | // ...
1068 | }
1069 | ```
1070 |
1071 | ### Configuring a WebSocket Proxy
1072 |
1073 | When setting up a WebSocket proxy, there are a some extra considerations to be aware of.
1074 |
1075 | If you’re using a WebSocket engine like [Socket.io](https://socket.io/), you must have a Socket.io server running that you can use as the proxy target. Socket.io will not work with a standard WebSocket server. Specifically, don't expect Socket.io to work with [the websocket.org echo test](http://websocket.org/echo.html).
1076 |
1077 | There’s some good documentation available for [setting up a Socket.io server](https://socket.io/docs/).
1078 |
1079 | Standard WebSockets **will** work with a standard WebSocket server as well as the websocket.org echo test. You can use libraries like [ws](https://github.com/websockets/ws) for the server, with [native WebSockets in the browser](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket).
1080 |
1081 | Either way, you can proxy WebSocket requests manually in `package.json`:
1082 |
1083 | ```js
1084 | {
1085 | // ...
1086 | "proxy": {
1087 | "/socket": {
1088 | // Your compatible WebSocket server
1089 | "target": "ws://",
1090 | // Tell http-proxy-middleware that this is a WebSocket proxy.
1091 | // Also allows you to proxy WebSocket requests without an additional HTTP request
1092 | // https://github.com/chimurai/http-proxy-middleware#external-websocket-upgrade
1093 | "ws": true
1094 | // ...
1095 | }
1096 | }
1097 | // ...
1098 | }
1099 | ```
1100 |
1101 | ## Using HTTPS in Development
1102 |
1103 | >Note: this feature is available with `react-scripts@0.4.0` and higher.
1104 |
1105 | You may require the dev server to serve pages over HTTPS. One particular case where this could be useful is when using [the "proxy" feature](#proxying-api-requests-in-development) to proxy requests to an API server when that API server is itself serving HTTPS.
1106 |
1107 | To do this, set the `HTTPS` environment variable to `true`, then start the dev server as usual with `npm start`:
1108 |
1109 | #### Windows (cmd.exe)
1110 |
1111 | ```cmd
1112 | set HTTPS=true&&npm start
1113 | ```
1114 |
1115 | (Note: the lack of whitespace is intentional.)
1116 |
1117 | #### Linux, macOS (Bash)
1118 |
1119 | ```bash
1120 | HTTPS=true npm start
1121 | ```
1122 |
1123 | Note that the server will use a self-signed certificate, so your web browser will almost definitely display a warning upon accessing the page.
1124 |
1125 | ## Generating Dynamic `` Tags on the Server
1126 |
1127 | Since Create React App doesn’t support server rendering, you might be wondering how to make `` tags dynamic and reflect the current URL. To solve this, we recommend to add placeholders into the HTML, like this:
1128 |
1129 | ```html
1130 |
1131 |
1132 |
1133 |
1134 |
1135 | ```
1136 |
1137 | Then, on the server, regardless of the backend you use, you can read `index.html` into memory and replace `__OG_TITLE__`, `__OG_DESCRIPTION__`, and any other placeholders with values depending on the current URL. Just make sure to sanitize and escape the interpolated values so that they are safe to embed into HTML!
1138 |
1139 | If you use a Node server, you can even share the route matching logic between the client and the server. However duplicating it also works fine in simple cases.
1140 |
1141 | ## Pre-Rendering into Static HTML Files
1142 |
1143 | If you’re hosting your `build` with a static hosting provider you can use [react-snapshot](https://www.npmjs.com/package/react-snapshot) to generate HTML pages for each route, or relative link, in your application. These pages will then seamlessly become active, or “hydrated”, when the JavaScript bundle has loaded.
1144 |
1145 | There are also opportunities to use this outside of static hosting, to take the pressure off the server when generating and caching routes.
1146 |
1147 | The primary benefit of pre-rendering is that you get the core content of each page _with_ the HTML payload—regardless of whether or not your JavaScript bundle successfully downloads. It also increases the likelihood that each route of your application will be picked up by search engines.
1148 |
1149 | You can read more about [zero-configuration pre-rendering (also called snapshotting) here](https://medium.com/superhighfives/an-almost-static-stack-6df0a2791319).
1150 |
1151 | ## Injecting Data from the Server into the Page
1152 |
1153 | Similarly to the previous section, you can leave some placeholders in the HTML that inject global variables, for example:
1154 |
1155 | ```js
1156 |
1157 |
1158 |
1159 |
1162 | ```
1163 |
1164 | Then, on the server, you can replace `__SERVER_DATA__` with a JSON of real data right before sending the response. The client code can then read `window.SERVER_DATA` to use it. **Make sure to [sanitize the JSON before sending it to the client](https://medium.com/node-security/the-most-common-xss-vulnerability-in-react-js-applications-2bdffbcc1fa0) as it makes your app vulnerable to XSS attacks.**
1165 |
1166 | ## Running Tests
1167 |
1168 | >Note: this feature is available with `react-scripts@0.3.0` and higher.
1169 | >[Read the migration guide to learn how to enable it in older projects!](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md#migrating-from-023-to-030)
1170 |
1171 | Create React App uses [Jest](https://facebook.github.io/jest/) as its test runner. To prepare for this integration, we did a [major revamp](https://facebook.github.io/jest/blog/2016/09/01/jest-15.html) of Jest so if you heard bad things about it years ago, give it another try.
1172 |
1173 | Jest is a Node-based runner. This means that the tests always run in a Node environment and not in a real browser. This lets us enable fast iteration speed and prevent flakiness.
1174 |
1175 | While Jest provides browser globals such as `window` thanks to [jsdom](https://github.com/tmpvar/jsdom), they are only approximations of the real browser behavior. Jest is intended to be used for unit tests of your logic and your components rather than the DOM quirks.
1176 |
1177 | We recommend that you use a separate tool for browser end-to-end tests if you need them. They are beyond the scope of Create React App.
1178 |
1179 | ### Filename Conventions
1180 |
1181 | Jest will look for test files with any of the following popular naming conventions:
1182 |
1183 | * Files with `.js` suffix in `__tests__` folders.
1184 | * Files with `.test.js` suffix.
1185 | * Files with `.spec.js` suffix.
1186 |
1187 | The `.test.js` / `.spec.js` files (or the `__tests__` folders) can be located at any depth under the `src` top level folder.
1188 |
1189 | We recommend to put the test files (or `__tests__` folders) next to the code they are testing so that relative imports appear shorter. For example, if `App.test.js` and `App.js` are in the same folder, the test just needs to `import App from './App'` instead of a long relative path. Colocation also helps find tests more quickly in larger projects.
1190 |
1191 | ### Command Line Interface
1192 |
1193 | When you run `npm test`, Jest will launch in the watch mode. Every time you save a file, it will re-run the tests, just like `npm start` recompiles the code.
1194 |
1195 | The watcher includes an interactive command-line interface with the ability to run all tests, or focus on a search pattern. It is designed this way so that you can keep it open and enjoy fast re-runs. You can learn the commands from the “Watch Usage” note that the watcher prints after every run:
1196 |
1197 | 
1198 |
1199 | ### Version Control Integration
1200 |
1201 | By default, when you run `npm test`, Jest will only run the tests related to files changed since the last commit. This is an optimization designed to make your tests run fast regardless of how many tests you have. However it assumes that you don’t often commit the code that doesn’t pass the tests.
1202 |
1203 | Jest will always explicitly mention that it only ran tests related to the files changed since the last commit. You can also press `a` in the watch mode to force Jest to run all tests.
1204 |
1205 | Jest will always run all tests on a [continuous integration](#continuous-integration) server or if the project is not inside a Git or Mercurial repository.
1206 |
1207 | ### Writing Tests
1208 |
1209 | To create tests, add `it()` (or `test()`) blocks with the name of the test and its code. You may optionally wrap them in `describe()` blocks for logical grouping but this is neither required nor recommended.
1210 |
1211 | Jest provides a built-in `expect()` global function for making assertions. A basic test could look like this:
1212 |
1213 | ```js
1214 | import sum from './sum';
1215 |
1216 | it('sums numbers', () => {
1217 | expect(sum(1, 2)).toEqual(3);
1218 | expect(sum(2, 2)).toEqual(4);
1219 | });
1220 | ```
1221 |
1222 | All `expect()` matchers supported by Jest are [extensively documented here](http://facebook.github.io/jest/docs/expect.html).
1223 | You can also use [`jest.fn()` and `expect(fn).toBeCalled()`](http://facebook.github.io/jest/docs/expect.html#tohavebeencalled) to create “spies” or mock functions.
1224 |
1225 | ### Testing Components
1226 |
1227 | There is a broad spectrum of component testing techniques. They range from a “smoke test” verifying that a component renders without throwing, to shallow rendering and testing some of the output, to full rendering and testing component lifecycle and state changes.
1228 |
1229 | Different projects choose different testing tradeoffs based on how often components change, and how much logic they contain. If you haven’t decided on a testing strategy yet, we recommend that you start with creating simple smoke tests for your components:
1230 |
1231 | ```js
1232 | import React from 'react';
1233 | import ReactDOM from 'react-dom';
1234 | import App from './App';
1235 |
1236 | it('renders without crashing', () => {
1237 | const div = document.createElement('div');
1238 | ReactDOM.createRoot(, div);
1239 | });
1240 | ```
1241 |
1242 | This test mounts a component and makes sure that it didn’t throw during rendering. Tests like this provide a lot value with very little effort so they are great as a starting point, and this is the test you will find in `src/App.test.js`.
1243 |
1244 | When you encounter bugs caused by changing components, you will gain a deeper insight into which parts of them are worth testing in your application. This might be a good time to introduce more specific tests asserting specific expected output or behavior.
1245 |
1246 | If you’d like to test components in isolation from the child components they render, we recommend using [`shallow()` rendering API](http://airbnb.io/enzyme/docs/api/shallow.html) from [Enzyme](http://airbnb.io/enzyme/). To install it, run:
1247 |
1248 | ```sh
1249 | npm install --save enzyme react-test-renderer
1250 | ```
1251 |
1252 | Alternatively you may use `yarn`:
1253 |
1254 | ```sh
1255 | yarn add enzyme react-test-renderer
1256 | ```
1257 |
1258 | You can write a smoke test with it too:
1259 |
1260 | ```js
1261 | import React from 'react';
1262 | import { shallow } from 'enzyme';
1263 | import App from './App';
1264 |
1265 | it('renders without crashing', () => {
1266 | shallow();
1267 | });
1268 | ```
1269 |
1270 | Unlike the previous smoke test using `ReactDOM.render()`, this test only renders `` and doesn’t go deeper. For example, even if `` itself renders a `