Front-End Build for React SPAs

This document explains the details of the project created when using the archetype to create a single page application (SPA) based on the React framework. I.e. when you set the frontendModule option to react.

Overview

This project was bootstrapped with create-react-app.

This application is built to consume the AEM model of a site. It will automatically generate the layout using the helper components from the @adobe/cq-react-editable-components package.

Scripts

In the project directory, you can run the following commands:

npm start

npm start

This command runs the app in development mode by proxying the JSON model from a local AEM instance running at http://localhost:4502. This assumes that the entire project has been deployed to AEM at least once (mvn clean install -PautoInstallPackage in the project root).

After running npm start in the ui.frontend directory, your app will be automatically opened in your browser (at path http://localhost:3000/content/<appId>/<country>/<language>/home.html). If you make edits, the page will reload.

If you are getting errors related to CORS, you might want to configure AEM as follows:

  1. Navigate to the Configuration Manager (http://localhost:4502/system/console/configMgr)
  2. Open the configuration for “Adobe Granite Cross-Origin Resource Sharing Policy”
  3. Create a new configuration with the following additional values:
    • Allowed Origins: http://localhost:3000
    • Supported Headers: Authorization
    • Allowed Methods: OPTIONS

npm test

npm test

This command launches the test runner in the interactive watch mode. See the React documentation about running tests for more information.

npm run build

npm run build

This command builds the app for production to the build folder. It bundles React in production mode and optimizes the build for the best performance. See the React documentation about deployment for more information.

Furthermore, an AEM ClientLib is generated from the app using the aem-clientlib-generator package.

Browser Support

By default, this project uses Browserslist’s defaults option to identify target browsers. Additionally, it includes polyfills for modern language features to support older browsers (e.g. Internet Explorer 11). If supporting such browsers isn’t a requirement, the polyfill dependencies and imports can be removed.

Code Splitting

The React app is configured to make use of code splitting by default. When building the app for production, the code will be output in several chunks:

$ ls build/static/js
2.5b77f553.chunk.js
2.5b77f553.chunk.js.map
main.cff1a559.chunk.js
main.cff1a559.chunk.js.map
runtime~main.a8a9905a.js
runtime~main.a8a9905a.js.map

Loading chunks only when they are required can improve the app performance significantly.

For this feature to work with AEM, the app needs to be able to identify which JS and CSS files need to be requested from the HTML generated by AEM. This can be achieved using the “entrypoints” key in the asset-manifest.json file. The file is parsed in clientlib.config.js and only the entrypoint files are bundled into the ClientLib. The remaining files are placed in the ClientLib’s resources directory and will be requested dynamically and therefore only loaded when they are actually needed.

See the general ui.frontend module documentation for further information about how AEM ClientLibs are used by the project archetype.

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