├── public
    ├── favicon.ico
    ├── logo192.png
    ├── logo512.png
    ├── robots.txt
    ├── config.js
    ├── manifest.json
    └── index.html
├── src
    ├── feature-toggles.js
    ├── App.test.js
    ├── setupTests.js
    ├── index.css
    ├── dev-tools
    │   ├── dev-tools.css
    │   ├── feature-toggles.js
    │   ├── load.js
    │   ├── dev-tools.local-example.js
    │   └── dev-tools.js
    ├── index.js
    ├── App.css
    ├── logo.svg
    └── App.js
├── .gitignore
├── README.md
└── package.json


/public/favicon.ico:
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https://raw.githubusercontent.com/kentcdodds/app-dev-tools/HEAD/public/favicon.ico


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/public/logo192.png:
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https://raw.githubusercontent.com/kentcdodds/app-dev-tools/HEAD/public/logo192.png


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/public/logo512.png:
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https://raw.githubusercontent.com/kentcdodds/app-dev-tools/HEAD/public/logo512.png


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/public/robots.txt:
--------------------------------------------------------------------------------
1 | # https://www.robotstxt.org/robotstxt.html
2 | User-agent: *
3 | Disallow:
4 | 


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/public/config.js:
--------------------------------------------------------------------------------
1 | // pretend that this is dynamically generated via a server
2 | 
3 | window.APP_CONFIG = {
4 |   featureToggles: {},
5 | }
6 | 


--------------------------------------------------------------------------------
/src/feature-toggles.js:
--------------------------------------------------------------------------------
1 | // APP_CONFIG is set via the `config.js` script that's in /public
2 | const featureToggles = window.APP_CONFIG.featureToggles
3 | 
4 | export default featureToggles
5 | 


--------------------------------------------------------------------------------
/src/App.test.js:
--------------------------------------------------------------------------------
 1 | import React from 'react'
 2 | import {render} from '@testing-library/react'
 3 | import App from './App'
 4 | 
 5 | test('renders learn react link', () => {
 6 |   const {getByText} = render(<App />)
 7 |   const linkElement = getByText(/learn about react/i)
 8 |   expect(linkElement).toBeInTheDocument()
 9 | })
10 | 


--------------------------------------------------------------------------------
/src/setupTests.js:
--------------------------------------------------------------------------------
1 | // jest-dom adds custom jest matchers for asserting on DOM nodes.
2 | // allows you to do things like:
3 | // expect(element).toHaveTextContent(/react/i)
4 | // learn more: https://github.com/testing-library/jest-dom
5 | import '@testing-library/jest-dom/extend-expect'
6 | 
7 | window.APP_CONFIG = {featureToggles: {}}
8 | 


--------------------------------------------------------------------------------
/src/index.css:
--------------------------------------------------------------------------------
 1 | body {
 2 |   margin: 0;
 3 |   font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
 4 |     'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
 5 |     sans-serif;
 6 |   -webkit-font-smoothing: antialiased;
 7 |   -moz-osx-font-smoothing: grayscale;
 8 | }
 9 | 
10 | code {
11 |   font-family: source-code-pro, Menlo, Monaco, Consolas, 'Courier New',
12 |     monospace;
13 | }
14 | 


--------------------------------------------------------------------------------
/.gitignore:
--------------------------------------------------------------------------------
 1 | # See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
 2 | 
 3 | # dependencies
 4 | /node_modules
 5 | /.pnp
 6 | .pnp.js
 7 | 
 8 | # testing
 9 | /coverage
10 | 
11 | # production
12 | /build
13 | 
14 | # misc
15 | .DS_Store
16 | .env.local
17 | .env.development.local
18 | .env.test.local
19 | .env.production.local
20 | 
21 | npm-debug.log*
22 | yarn-debug.log*
23 | yarn-error.log*
24 | 
25 | *.local.*


--------------------------------------------------------------------------------
/src/dev-tools/dev-tools.css:
--------------------------------------------------------------------------------
 1 | #dev-tools {
 2 |   position: absolute;
 3 |   bottom: 0;
 4 |   background: black;
 5 |   opacity: 0.4;
 6 |   color: white;
 7 |   width: 100%;
 8 |   padding: 20px;
 9 |   height: 60px;
10 |   width: 60px;
11 |   transition: all 0.3s;
12 | }
13 | 
14 | #dev-tools:hover {
15 |   height: 300px;
16 |   width: 100%;
17 |   opacity: 0.9;
18 | }
19 | 
20 | #dev-tools .tools {
21 |   display: none;
22 | }
23 | 
24 | #dev-tools:hover .tools {
25 |   display: block;
26 | }
27 | 


--------------------------------------------------------------------------------
/src/index.js:
--------------------------------------------------------------------------------
 1 | import loadDevTools from './dev-tools/load'
 2 | import React from 'react'
 3 | import ReactDOM from 'react-dom'
 4 | import './index.css'
 5 | import App from './App'
 6 | 
 7 | // load and install the dev tools (if they need to be)
 8 | // and when that's done, let's render the app
 9 | // NOTE: if we don't need to install the devtools, then the callback
10 | // is called synchronously so there's no penalty for including this
11 | // in production.
12 | loadDevTools(() => {
13 |   ReactDOM.render(<App />, document.getElementById('root'))
14 | })
15 | 


--------------------------------------------------------------------------------
/public/manifest.json:
--------------------------------------------------------------------------------
 1 | {
 2 |   "short_name": "React App",
 3 |   "name": "Create React App Sample",
 4 |   "icons": [
 5 |     {
 6 |       "src": "favicon.ico",
 7 |       "sizes": "64x64 32x32 24x24 16x16",
 8 |       "type": "image/x-icon"
 9 |     },
10 |     {
11 |       "src": "logo192.png",
12 |       "type": "image/png",
13 |       "sizes": "192x192"
14 |     },
15 |     {
16 |       "src": "logo512.png",
17 |       "type": "image/png",
18 |       "sizes": "512x512"
19 |     }
20 |   ],
21 |   "start_url": ".",
22 |   "display": "standalone",
23 |   "theme_color": "#000000",
24 |   "background_color": "#ffffff"
25 | }
26 | 


--------------------------------------------------------------------------------
/src/App.css:
--------------------------------------------------------------------------------
 1 | .App {
 2 |   text-align: center;
 3 | }
 4 | 
 5 | .App-logo {
 6 |   font-size: 40vmin;
 7 |   height: 40vmin;
 8 |   pointer-events: none;
 9 | }
10 | 
11 | @media (prefers-reduced-motion: no-preference) {
12 |   .App-logo {
13 |     animation: App-logo-spin infinite 20s linear;
14 |   }
15 | }
16 | 
17 | .App-header {
18 |   background-color: #282c34;
19 |   min-height: 100vh;
20 |   display: flex;
21 |   flex-direction: column;
22 |   align-items: center;
23 |   justify-content: center;
24 |   font-size: calc(10px + 2vmin);
25 |   color: white;
26 | }
27 | 
28 | a {
29 |   color: #61dafb;
30 | }
31 | 
32 | @keyframes App-logo-spin {
33 |   from {
34 |     transform: rotate(0deg);
35 |   }
36 |   to {
37 |     transform: rotate(360deg);
38 |   }
39 | }
40 | 


--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
 1 | # App DevTools
 2 | 
 3 | A little demo of how you might implement custom App Developer Tools.
 4 | 
 5 | In this example, we're using custom DevTools to make it easy to enable/disable
 6 | ["feature toggles"](https://en.wikipedia.org/wiki/Feature_toggle). Please note
 7 | that the concept of App DevTools has WAY more applicability than just feature
 8 | toggles.
 9 | 
10 | Files to take a look at to learn how the feature toggles are implemented for
11 | this app:
12 | 
13 | - `public/config.js`
14 | - `public/index.html`
15 | - `src/feature-toggles.js`
16 | - `src/App.js`
17 | 
18 | Once you understand how the feature toggles work, then check out how the dev
19 | tools are installed and how they allow you to interact with the feature toggles
20 | by opening `src/index.js` and files in `src/dev-tools/`.
21 | 


--------------------------------------------------------------------------------
/src/dev-tools/feature-toggles.js:
--------------------------------------------------------------------------------
 1 | import featureToggles from '../feature-toggles'
 2 | 
 3 | const key = 'feature-toggles'
 4 | 
 5 | // update featureToggles with what's in localStorage
 6 | try {
 7 |   Object.assign(featureToggles, JSON.parse(window.localStorage.getItem(key)))
 8 | } catch (error) {
 9 |   window.localStorage.removeItem(key)
10 | }
11 | 
12 | const persist = () =>
13 |   window.localStorage.setItem(key, JSON.stringify(featureToggles))
14 | 
15 | function enable(name) {
16 |   console.log(featureToggles, name, 'enabling')
17 |   featureToggles[name] = true
18 |   persist()
19 | }
20 | 
21 | function disable(name) {
22 |   console.log(featureToggles, name, 'disabling')
23 |   featureToggles[name] = false
24 |   persist()
25 | }
26 | 
27 | export default featureToggles
28 | export {enable, disable}
29 | 


--------------------------------------------------------------------------------
/package.json:
--------------------------------------------------------------------------------
 1 | {
 2 |   "name": "app-dev-tools",
 3 |   "version": "0.1.0",
 4 |   "private": true,
 5 |   "dependencies": {
 6 |     "@testing-library/jest-dom": "^4.2.4",
 7 |     "@testing-library/react": "^9.3.2",
 8 |     "@testing-library/user-event": "^7.1.2",
 9 |     "react": "^16.12.0",
10 |     "react-dom": "^16.12.0",
11 |     "react-scripts": "3.4.0"
12 |   },
13 |   "scripts": {
14 |     "start": "react-scripts start",
15 |     "build": "react-scripts build",
16 |     "test": "react-scripts test",
17 |     "eject": "react-scripts eject"
18 |   },
19 |   "eslintConfig": {
20 |     "extends": "react-app"
21 |   },
22 |   "browserslist": {
23 |     "production": [
24 |       ">0.2%",
25 |       "not dead",
26 |       "not op_mini all"
27 |     ],
28 |     "development": [
29 |       "last 1 chrome version",
30 |       "last 1 firefox version",
31 |       "last 1 safari version"
32 |     ]
33 |   }
34 | }
35 | 


--------------------------------------------------------------------------------
/src/dev-tools/load.js:
--------------------------------------------------------------------------------
 1 | function loadDevTools(callback) {
 2 |   // this allows you to explicitly disable it in development for example
 3 |   const explicitlyDisabled =
 4 |     window.location.search.includes('dev-tools=false') ||
 5 |     window.localStorage.getItem('dev-tools') === 'false'
 6 | 
 7 |   const explicitlyEnabled =
 8 |     window.location.search.includes('dev-tools=true') ||
 9 |     window.localStorage.getItem('dev-tools') === 'true'
10 | 
11 |   // we want it enabled by default everywhere but production and we also want
12 |   // to support the dev tools in production (to make us more productive triaging production issues).
13 |   // you can enable the DevTools via localStorage or the query string.
14 |   if (
15 |     !explicitlyDisabled &&
16 |     (process.env.NODE_ENV === 'development' || explicitlyEnabled)
17 |   ) {
18 |     // use a dynamic import so the dev-tools code isn't bundled with the regular
19 |     // app code so we don't worry about bundle size.
20 |     import('./dev-tools')
21 |       .then(devTools => devTools.install())
22 |       .finally(callback)
23 |   } else {
24 |     // if we don't need the DevTools, call the callback immediately.
25 |     callback()
26 |   }
27 | }
28 | 
29 | export default loadDevTools
30 | 


--------------------------------------------------------------------------------
/src/dev-tools/dev-tools.local-example.js:
--------------------------------------------------------------------------------
 1 | // if you want to have custom dev tools, create a file right here called
 2 | // dev-tools.local.js.
 3 | // because the .gitignore lists *.local.* as ignored you can change anything
 4 | // you want in your local dev-tools file and it won't impact anyone else.
 5 | 
 6 | // Here's an example of some of the things you could do:
 7 | import React from 'react'
 8 | import {screen, waitForElementToBeRemoved} from '@testing-library/react'
 9 | import userEvent from '@testing-library/user-event'
10 | import {enable} from './feature-toggles'
11 | 
12 | // If I want to make sure that tacos is always enabled locally, I can uncomment this:
13 | enable('tacos')
14 | 
15 | // you can do whatever hackery you want in here.
16 | // Like you could use React Testing Library to fill out the username add password on load:
17 | async function automaticallyLogin() {
18 |   try {
19 |     await userEvent.type(await screen.findByLabelText(/username/i), 'FAKE_USER')
20 |     await userEvent.type(
21 |       await screen.findByLabelText(/password/i),
22 |       'FAKE_PASSWORD',
23 |     )
24 |     await userEvent.click(await screen.findByText(/submit/i))
25 |     await waitForElementToBeRemoved(() => screen.getByText(/loading/i))
26 |   } catch (error) {
27 |     //ignore the error because we're probably already logged in so no need
28 |   }
29 | }
30 | 
31 | automaticallyLogin()
32 | 
33 | // in the past I'd also have a history listener that would automatically execute
34 | // code when I navigated to a specific path (to auto-fill a large form I was
35 | // working on).
36 | 
37 | // This is an optional component I can export to add a tool to the DevTools UI
38 | export default () => <div>Local dev tools!</div>
39 | 


--------------------------------------------------------------------------------
/src/dev-tools/dev-tools.js:
--------------------------------------------------------------------------------
 1 | import './dev-tools.css'
 2 | import featureToggles, {enable, disable} from './feature-toggles'
 3 | import React from 'react'
 4 | import ReactDOM from 'react-dom'
 5 | 
 6 | function install() {
 7 |   window.devToolsEnabled = true
 8 |   // load local dev tools if it's there
 9 |   // NOTE: this is using some webpack-sepecific features.
10 |   // if you're not using webpack, you might consider using
11 |   // https://npm.im/preval.macro or https://npm.im/codegen.macro
12 |   const requireDevToolsLocal = require.context(
13 |     './',
14 |     false,
15 |     /dev-tools\.local\.js/,
16 |   )
17 |   const local = requireDevToolsLocal.keys()[0]
18 |   let LocalDevTools
19 |   if (local) {
20 |     LocalDevTools = requireDevToolsLocal(local).default
21 |   }
22 |   LocalDevTools = LocalDevTools || (() => null)
23 | 
24 |   function TacoTool() {
25 |     const [tacos, setTacos] = React.useState(featureToggles.tacos)
26 | 
27 |     React.useEffect(() => {
28 |       if (tacos) {
29 |         enable('tacos')
30 |       } else {
31 |         disable('tacos')
32 |       }
33 |     }, [tacos])
34 | 
35 |     return (
36 |       <div>
37 |         <label>
38 |           Enable Tacos:{' '}
39 |           <input
40 |             type="checkbox"
41 |             checked={tacos}
42 |             onChange={e => setTacos(e.target.checked)}
43 |           />
44 |         </label>
45 |       </div>
46 |     )
47 |   }
48 | 
49 |   function DevTools() {
50 |     return (
51 |       <div id="dev-tools">
52 |         <div>🛠</div>
53 |         <div className="tools">
54 |           <LocalDevTools />
55 |           <TacoTool />
56 |         </div>
57 |       </div>
58 |     )
59 |   }
60 | 
61 |   // add dev tools UI to the page
62 |   const devToolsRoot = document.createElement('div')
63 |   document.body.appendChild(devToolsRoot)
64 |   ReactDOM.render(<DevTools />, devToolsRoot)
65 | }
66 | 
67 | export {install}
68 | 


--------------------------------------------------------------------------------
/public/index.html:
--------------------------------------------------------------------------------
 1 | <!DOCTYPE html>
 2 | <html lang="en">
 3 |   <head>
 4 |     <meta charset="utf-8" />
 5 |     <link rel="icon" href="%PUBLIC_URL%/favicon.ico" />
 6 |     <meta name="viewport" content="width=device-width, initial-scale=1" />
 7 |     <meta name="theme-color" content="#000000" />
 8 |     <meta
 9 |       name="description"
10 |       content="Web site created using create-react-app"
11 |     />
12 |     <link rel="apple-touch-icon" href="%PUBLIC_URL%/logo192.png" />
13 |     <!--
14 |       manifest.json provides metadata used when your web app is installed on a
15 |       user's mobile device or desktop. See https://developers.google.com/web/fundamentals/web-app-manifest/
16 |     -->
17 |     <link rel="manifest" href="%PUBLIC_URL%/manifest.json" />
18 |     <!--
19 |       Notice the use of %PUBLIC_URL% in the tags above.
20 |       It will be replaced with the URL of the `public` folder during the build.
21 |       Only files inside the `public` folder can be referenced from the HTML.
22 | 
23 |       Unlike "/favicon.ico" or "favicon.ico", "%PUBLIC_URL%/favicon.ico" will
24 |       work correctly both with client-side routing and a non-root public URL.
25 |       Learn how to configure a non-root public URL by running `npm run build`.
26 |     -->
27 |     <title>React App</title>
28 |     <style>
29 |       * {
30 |         box-sizing: border-box;
31 |       }
32 |     </style>
33 |     <script type="text/javascript" src="/config.js"></script>
34 |   </head>
35 |   <body>
36 |     <noscript>You need to enable JavaScript to run this app.</noscript>
37 |     <div id="root"></div>
38 |     <!--
39 |       This HTML file is a template.
40 |       If you open it directly in the browser, you will see an empty page.
41 | 
42 |       You can add webfonts, meta tags, or analytics to this file.
43 |       The build step will place the bundled scripts into the <body> tag.
44 | 
45 |       To begin the development, run `npm start` or `yarn start`.
46 |       To create a production bundle, use `npm run build` or `yarn build`.
47 |     -->
48 |   </body>
49 | </html>
50 | 


--------------------------------------------------------------------------------
/src/logo.svg:
--------------------------------------------------------------------------------
1 | <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 841.9 595.3">
2 |     <g fill="#61DAFB">
3 |         <path d="M666.3 296.5c0-32.5-40.7-63.3-103.1-82.4 14.4-63.6 8-114.2-20.2-130.4-6.5-3.8-14.1-5.6-22.4-5.6v22.3c4.6 0 8.3.9 11.4 2.6 13.6 7.8 19.5 37.5 14.9 75.7-1.1 9.4-2.9 19.3-5.1 29.4-19.6-4.8-41-8.5-63.5-10.9-13.5-18.5-27.5-35.3-41.6-50 32.6-30.3 63.2-46.9 84-46.9V78c-27.5 0-63.5 19.6-99.9 53.6-36.4-33.8-72.4-53.2-99.9-53.2v22.3c20.7 0 51.4 16.5 84 46.6-14 14.7-28 31.4-41.3 49.9-22.6 2.4-44 6.1-63.6 11-2.3-10-4-19.7-5.2-29-4.7-38.2 1.1-67.9 14.6-75.8 3-1.8 6.9-2.6 11.5-2.6V78.5c-8.4 0-16 1.8-22.6 5.6-28.1 16.2-34.4 66.7-19.9 130.1-62.2 19.2-102.7 49.9-102.7 82.3 0 32.5 40.7 63.3 103.1 82.4-14.4 63.6-8 114.2 20.2 130.4 6.5 3.8 14.1 5.6 22.5 5.6 27.5 0 63.5-19.6 99.9-53.6 36.4 33.8 72.4 53.2 99.9 53.2 8.4 0 16-1.8 22.6-5.6 28.1-16.2 34.4-66.7 19.9-130.1 62-19.1 102.5-49.9 102.5-82.3zm-130.2-66.7c-3.7 12.9-8.3 26.2-13.5 39.5-4.1-8-8.4-16-13.1-24-4.6-8-9.5-15.8-14.4-23.4 14.2 2.1 27.9 4.7 41 7.9zm-45.8 106.5c-7.8 13.5-15.8 26.3-24.1 38.2-14.9 1.3-30 2-45.2 2-15.1 0-30.2-.7-45-1.9-8.3-11.9-16.4-24.6-24.2-38-7.6-13.1-14.5-26.4-20.8-39.8 6.2-13.4 13.2-26.8 20.7-39.9 7.8-13.5 15.8-26.3 24.1-38.2 14.9-1.3 30-2 45.2-2 15.1 0 30.2.7 45 1.9 8.3 11.9 16.4 24.6 24.2 38 7.6 13.1 14.5 26.4 20.8 39.8-6.3 13.4-13.2 26.8-20.7 39.9zm32.3-13c5.4 13.4 10 26.8 13.8 39.8-13.1 3.2-26.9 5.9-41.2 8 4.9-7.7 9.8-15.6 14.4-23.7 4.6-8 8.9-16.1 13-24.1zM421.2 430c-9.3-9.6-18.6-20.3-27.8-32 9 .4 18.2.7 27.5.7 9.4 0 18.7-.2 27.8-.7-9 11.7-18.3 22.4-27.5 32zm-74.4-58.9c-14.2-2.1-27.9-4.7-41-7.9 3.7-12.9 8.3-26.2 13.5-39.5 4.1 8 8.4 16 13.1 24 4.7 8 9.5 15.8 14.4 23.4zM420.7 163c9.3 9.6 18.6 20.3 27.8 32-9-.4-18.2-.7-27.5-.7-9.4 0-18.7.2-27.8.7 9-11.7 18.3-22.4 27.5-32zm-74 58.9c-4.9 7.7-9.8 15.6-14.4 23.7-4.6 8-8.9 16-13 24-5.4-13.4-10-26.8-13.8-39.8 13.1-3.1 26.9-5.8 41.2-7.9zm-90.5 125.2c-35.4-15.1-58.3-34.9-58.3-50.6 0-15.7 22.9-35.6 58.3-50.6 8.6-3.7 18-7 27.7-10.1 5.7 19.6 13.2 40 22.5 60.9-9.2 20.8-16.6 41.1-22.2 60.6-9.9-3.1-19.3-6.5-28-10.2zM310 490c-13.6-7.8-19.5-37.5-14.9-75.7 1.1-9.4 2.9-19.3 5.1-29.4 19.6 4.8 41 8.5 63.5 10.9 13.5 18.5 27.5 35.3 41.6 50-32.6 30.3-63.2 46.9-84 46.9-4.5-.1-8.3-1-11.3-2.7zm237.2-76.2c4.7 38.2-1.1 67.9-14.6 75.8-3 1.8-6.9 2.6-11.5 2.6-20.7 0-51.4-16.5-84-46.6 14-14.7 28-31.4 41.3-49.9 22.6-2.4 44-6.1 63.6-11 2.3 10.1 4.1 19.8 5.2 29.1zm38.5-66.7c-8.6 3.7-18 7-27.7 10.1-5.7-19.6-13.2-40-22.5-60.9 9.2-20.8 16.6-41.1 22.2-60.6 9.9 3.1 19.3 6.5 28.1 10.2 35.4 15.1 58.3 34.9 58.3 50.6-.1 15.7-23 35.6-58.4 50.6zM320.8 78.4z"/>
4 |         <circle cx="420.9" cy="296.5" r="45.7"/>
5 |         <path d="M520.5 78.1z"/>
6 |     </g>
7 | </svg>
8 | 


--------------------------------------------------------------------------------
/src/App.js:
--------------------------------------------------------------------------------
 1 | import React from 'react'
 2 | import featureToggles from './feature-toggles'
 3 | import logo from './logo.svg'
 4 | import './App.css'
 5 | 
 6 | function App() {
 7 |   return (
 8 |     <div className="App">
 9 |       <header className="App-header">
10 |         {featureToggles.tacos ? (
11 |           <span className="App-logo" role="img" aria-label="taco">
12 |             🌮
13 |           </span>
14 |         ) : (
15 |           <img src={logo} className="App-logo" alt="logo" />
16 |         )}
17 |         <a
18 |           className="App-link"
19 |           href={
20 |             featureToggles.tacos
21 |               ? 'https://en.wikipedia.org/wiki/Taco'
22 |               : 'https://reactjs.org'
23 |           }
24 |           target="_blank"
25 |           rel="noopener noreferrer"
26 |         >
27 |           Learn about {featureToggles.tacos ? ' Tacos' : ' React'}
28 |         </a>
29 |         <p>
30 |           This is just a demo for DevTools.{' '}
31 |           {window.devToolsEnabled ? (
32 |             <>
33 |               DevTools are enabled. The UI for the DevTools appears in the
34 |               bottom left. Add{' '}
35 |               <a href="/?dev-tools=false">
36 |                 "<code>?dev-tools=false</code>"
37 |               </a>{' '}
38 |               to the URL to explicitely disable them (though in production they
39 |               are disabled by default)
40 |             </>
41 |           ) : (
42 |             <>
43 |               DevTools are disabled. Add{' '}
44 |               <a href="/?dev-tools=true">
45 |                 "<code>?dev-tools=true</code>"
46 |               </a>{' '}
47 |               to the URL to explicitely enable them (though in development they
48 |               are enabled by default). The DevTools UI will appear in the bottom
49 |               left.
50 |             </>
51 |           )}
52 |         </p>
53 |         {process.env.NODE_ENV === 'production' ? (
54 |           <p>
55 |             Notice that these work even in production! But it doesn't cost
56 |             anything to have them available for users who don't use them. Read
57 |             the blog post to learn how.
58 |           </p>
59 |         ) : null}
60 |         <p>
61 |           <a href="https://github.com/kentcdodds/app-dev-tools">
62 |             View Code on GitHub
63 |           </a>
64 |         </p>
65 |         <p>
66 |           Read{' '}
67 |           <a href="https://kentcdodds.com/blog/make-your-own-dev-tools">
68 |             the blog post.
69 |           </a>
70 |         </p>
71 |         <p>
72 |           Watch{' '}
73 |           <a href="https://egghead.io/lessons/javascript-create-app-devtools-to-enhance-development-productivity?pl=kent-s-blog-posts-as-screencasts-eefa540c&af=5236ad">
74 |             the video.
75 |           </a>
76 |         </p>
77 |       </header>
78 |     </div>
79 |   )
80 | }
81 | 
82 | export default App
83 | 


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