48 | Open [http://localhost:3000](http://localhost:3000) to view it in the browser. 49 | 50 | The page will reload if you make edits.
51 | You will also see any lint errors in the console. 52 | 53 | ### `npm run build` 54 | 55 | Builds the app for production to the `build` folder.
56 | It correctly bundles React in production mode and optimizes the build for the best performance. 57 | 58 | The build is minified and the filenames include the hashes.
59 | Your app is ready to be deployed! 60 | 61 | ### `npm run eject` 62 | 63 | **Note: this is a one-way operation. Once you `eject`, you can’t go back!** 64 | 65 | 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. 66 | 67 | Instead, it will copy all the configuration files and the transient 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. 68 | 69 | 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. 70 | 71 | ## How To... 72 | 73 | ### Import a Component 74 | 75 | This project setup supports ES6 modules thanks to Babel. 76 | 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. 77 | 78 | For example: 79 | 80 | ### `Button.js` 81 | 82 | ```js 83 | import React, { Component } from 'react'; 84 | 85 | class Button extends Component { 86 | render() { 87 | // ... 88 | } 89 | } 90 | 91 | export default Button; // Don’t forget to use export default! 92 | ``` 93 | 94 | ### `DangerButton.js` 95 | 96 | ```js 97 | import React, { Component } from 'react'; 98 | import Button from './Button'; // Import a component from another file 99 | 100 | class DangerButton extends Component { 101 | render() { 102 | return ; 103 | } 104 | } 105 | 106 | export default DangerButton; 107 | ``` 108 | 109 | 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. 110 | 111 | 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'`. 112 | 113 | 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. 114 | 115 | Learn more about ES6 modules: 116 | 117 | * [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) 118 | * [Exploring ES6: Modules](http://exploringjs.com/es6/ch_modules.html) 119 | * [Understanding ES6: Modules](https://leanpub.com/understandinges6/read#leanpub-auto-encapsulating-code-with-modules) 120 | 121 | ### Add a Stylesheet 122 | 123 | This project setup uses [Webpack](https://webpack.github.io/) 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**: 124 | 125 | #### `Button.css` 126 | 127 | ```css 128 | .Button { 129 | padding: 20px; 130 | } 131 | ``` 132 | 133 | #### `Button.js` 134 | 135 | ```js 136 | import React, { Component } from 'react'; 137 | import './Button.css'; // Tell Webpack that Button.js uses these styles 138 | 139 | class Button extends Component { 140 | render() { 141 | // You can use them as regular CSS styles 142 | return ; 143 | } 144 | } 145 | ``` 146 | 147 | **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. 148 | 149 | 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. 150 | 151 | 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. 152 | 153 | ### Post-Process CSS 154 | 155 | 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. 156 | 157 | For example, this: 158 | 159 | ```css 160 | .App { 161 | display: flex; 162 | flex-direction: row; 163 | align-items: center; 164 | } 165 | ``` 166 | 167 | becomes this: 168 | 169 | ```css 170 | .App { 171 | display: -webkit-box; 172 | display: -ms-flexbox; 173 | display: flex; 174 | -webkit-box-orient: horizontal; 175 | -webkit-box-direction: normal; 176 | -ms-flex-direction: row; 177 | flex-direction: row; 178 | -webkit-box-align: center; 179 | -ms-flex-align: center; 180 | align-items: center; 181 | } 182 | ``` 183 | 184 | There is currently no support for preprocessors such as Less, or for sharing variables across CSS files. 185 | 186 | ### Add Images and Fonts 187 | 188 | With Webpack, using static assets like images and fonts works similarly to CSS. 189 | 190 | You can **`import` an image right in a JavaScript module**. This tells Webpack to include that image in the bundle. Unlike CSS imports, importing an image or a font gives you a string value. This value is the final image path you can reference in your code. 191 | 192 | Here is an example: 193 | 194 | ```js 195 | import React from 'react'; 196 | import logo from './logo.png'; // Tell Webpack this JS file uses this image 197 | 198 | console.log(logo); // /84287d09b8053c6fa598893b8910786a.png 199 | 200 | function Header() { 201 | // Import result is the URL of your image 202 | return
9 |
17 | );
18 | }
19 | }
20 |
21 | export default App;
22 |
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/template/src/index.css:
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1 | body {
2 | margin: 0;
3 | padding: 0;
4 | font-family: sans-serif;
5 | }
6 |
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/template/src/index.js:
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1 | import React from 'react';
2 | import ReactDOM from 'react-dom';
3 | import App from './App';
4 | import './index.css';
5 |
6 | ReactDOM.render(
7 |
10 | 
11 |
13 | Welcome to React
12 |
14 | To get started, edit src/App.js and save to reload.
15 |