Dapparatus

The NODE_ENV variable is a built-in environment variable that tells you the current execution mode. You cannot override it manually.

• npm start sets NODE_ENV to 'development'
• npm test sets NODE_ENV to 'test'
• npm run build sets NODE_ENV to 'production'

Use this to perform actions conditionally, such as disabling analytics in development or stripping code during minification in production.

if (process.env.NODE_ENV !== 'production') {
  analytics.disable();
}

To enable debugging in VS Code, ensure you have the latest version of VS Code and the Chrome Debugger Extension installed.

Create a .vscode/launch.json file in your app's root directory and add the following configuration:

1. Start your app with npm start.
2. Press F5 or click the green debug icon in VS Code to start debugging.

Note: If you have changed the HOST or PORT environment variables, update the url field in the configuration accordingly.

{
  "version": "0.2.0",
  "configurations": [{
    "name": "Chrome",
    "type": "chrome",
    "request": "launch",
    "url": "http://localhost:3000",
    "webRoot": "${workspaceRoot}/src",
    "sourceMapPathOverrides": {
      "webpack:///src/*": "${webRoot}/*"
    }
  }]
}

To prevent downloading the entire application at once, you can use dynamic import() to load code chunks on demand. The import() function returns a Promise that resolves to the module's namespace object. This is useful for loading heavy components or modules only when a specific user action occurs.

You can use either .then() syntax or async/await syntax.

// moduleA.js
const moduleA = 'Hello';
export { moduleA };

// App.js
import React, { Component } from 'react';

class App extends Component {
  handleClick = () => {
    import('./moduleA')
      .then(({ moduleA }) => {
        // Use moduleA
      })
      .catch(err => {
        // Handle failure
      });
  };

  render() {
    return (
      <div>
        <button onClick={this.handleClick}>Load</button>
      </div>
    );
  }
}

export default App;

Since Create React App does not support server-side rendering, you can implement dynamic <meta> tags (for SEO/social sharing) by using placeholders in your index.html and replacing them on your server before sending the response.

Example pattern:

1. Add placeholders like __OG_TITLE__ to index.html.
2. On your backend, read the file, replace placeholders with sanitized values, and serve the modified HTML.

Security Note: Always sanitize and escape interpolated values to prevent XSS attacks.

<head>
  <meta property="og:title" content="__OG_TITLE__">
  <meta property="og:description" content="__OG_DESCRIPTION__">
</head>

Files in the public folder are not processed by Webpack and are copied to the build folder untouched. To reference these assets, use the %PUBLIC_URL% variable in HTML or process.env.PUBLIC_URL in JavaScript. This is an 'escape hatch' for cases like manifest files, large numbers of dynamic images, or scripts incompatible with Webpack.

Downsides:

• No minification or post-processing.
• No content hashes (requires manual cache busting).
• Missing files cause 404s at runtime rather than compilation errors.

<!-- In index.html -->
<link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">

<!-- In JavaScript -->
<img src={process.env.PUBLIC_URL + '/img/logo.png'} />

The project includes a polyfill for the browser fetch() API and a Promise polyfill, allowing you to use fetch() and async/await syntax reliably. You can also use libraries like axios for AJAX requests.

// Example using fetch with async/await
async function fetchData() {
  const response = await fetch('https://api.example.com/data');
  const data = await response.json();
  return data;
}

The demoapp project uses react-scripts as its development dependency. To update an existing project, you should check your current version in package.json and compare it against the Create React App changelog for migration instructions.

In most cases, you can update by bumping the react-scripts version in package.json and running npm install.

The production build is configured as an offline-first Progressive Web App using sw-precache-webpack-plugin.

To disable service workers before your initial production deployment, remove the call to registerServiceWorker() from src/index.js.

To disable service workers for existing users who already have them enabled, modify the service worker import in src/index.js to use unregister instead of register:

import { unregister } from './registerServiceWorker';

Then call unregister(). Note that it may take up to 24 hours for the cache to be invalidated depending on how /service-worker.js is served.

import { unregister } from './registerServiceWorker';

// Call unregister() instead of registerServiceWorker()
unregister();

React Styleguidist provides a style guide and an environment for developing components in isolation. It uses Markdown to document props and usage, rendering code snippets as live editable playgrounds.

To set up Styleguidist:

1. Install the package:

npm install --save react-styleguidist

2. Add the following scripts to your package.json:

"scripts": {
    "styleguide": "styleguidist server",
    "styleguide:build": "styleguidist build"
}

3. Run the server:

npm run styleguide

npm install --save react-styleguidist
# Add to package.json:
# "styleguide": "styleguidist server"
# "styleguide:build": "styleguidist build"
npm run styleguide

Now offers zero-configuration deployment:

1. Install the CLI: npm install -g now.
2. Build your app: npm run build.
3. Deploy from the build directory:

   cd build
   now --name your-project-name