This package includes some utilities used by Create React App.
Please refer to its documentation:
- Getting Started – How to create a new app.
- User Guide – How to develop apps bootstrapped with Create React App.
These utilities come by default with Create React App, which includes it by default. You don’t need to install it separately in Create React App projects.
If you don’t use Create React App, or if you ejected, you may keep using these utilities. Their development will be aligned with Create React App, so major versions of these utilities may come out relatively often. Feel free to fork or copy and paste them into your projects if you’d like to have more control over them, or feel free to use the old versions. Not all of them are React-specific, but we might make some of them more React-specific in the future.
There is no single entry point. You can only import individual top-level modules.
new InterpolateHtmlPlugin(htmlWebpackPlugin: HtmlWebpackPlugin, replacements: {[key:string]: string})
This Webpack plugin lets us interpolate custom variables into index.html.
It works in tandem with HtmlWebpackPlugin 2.x via its events.
var path = require('path');
var HtmlWebpackPlugin = require('html-webpack-plugin');
var InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
// Webpack config
var publicUrl = '/my-custom-url';
module.exports = {
output: {
// ...
publicPath: publicUrl + '/',
},
// ...
plugins: [
// Generates an `index.html` file with the <script> injected.
new HtmlWebpackPlugin({
inject: true,
template: path.resolve('public/index.html'),
}),
// Makes the public URL available as %PUBLIC_URL% in index.html, e.g.:
// <link rel="icon" href="%PUBLIC_URL%/favicon.ico">
new InterpolateHtmlPlugin(HtmlWebpackPlugin, {
PUBLIC_URL: publicUrl,
// You can pass any key-value pairs, this was just an example.
// WHATEVER: 42 will replace %WHATEVER% with 42 in index.html.
}),
// ...
],
// ...
};This Webpack plugin inlines script chunks into index.html.
It works in tandem with HtmlWebpackPlugin 4.x.
var path = require('path');
var HtmlWebpackPlugin = require('html-webpack-plugin');
var InlineChunkHtmlPlugin = require('react-dev-utils/InlineChunkHtmlPlugin');
// Webpack config
var publicUrl = '/my-custom-url';
module.exports = {
output: {
// ...
publicPath: publicUrl + '/',
},
// ...
plugins: [
// Generates an `index.html` file with the <script> injected.
new HtmlWebpackPlugin({
inject: true,
template: path.resolve('public/index.html'),
}),
// Inlines chunks with `runtime` in the name
new InlineChunkHtmlPlugin(HtmlWebpackPlugin, [/runtime/]),
// ...
],
// ...
};This Webpack plugin ensures that relative imports from app's source directories don't reach outside of it.
var path = require('path');
var ModuleScopePlugin = require('react-dev-utils/ModuleScopePlugin');
module.exports = {
// ...
resolve: {
// ...
plugins: [
new ModuleScopePlugin(paths.appSrc, [paths.appPackageJson]),
// ...
],
// ...
},
// ...
};This Webpack plugin ensures npm install <library> forces a project rebuild.
We’re not sure why this isn't Webpack's default behavior.
See #186 for details.
var path = require('path');
var WatchMissingNodeModulesPlugin = require('react-dev-utils/WatchMissingNodeModulesPlugin');
// Webpack config
module.exports = {
// ...
plugins: [
// ...
// If you require a missing module and then `npm install` it, you still have
// to restart the development server for Webpack to discover it. This plugin
// makes the discovery automatic so you don't have to restart.
// See https://github.com/facebook/create-react-app/issues/186
new WatchMissingNodeModulesPlugin(path.resolve('node_modules')),
],
// ...
};Makes sure that all passed files exist.
Filenames are expected to be absolute.
If a file is not found, prints a warning message and returns false.
var path = require('path');
var checkRequiredFiles = require('react-dev-utils/checkRequiredFiles');
if (
!checkRequiredFiles([
path.resolve('public/index.html'),
path.resolve('src/index.js'),
])
) {
process.exit(1);
}Clears the console, hopefully in a cross-platform way.
var clearConsole = require('react-dev-utils/clearConsole');
clearConsole();
console.log('Just cleared the screen!');This is our custom ESLint formatter that integrates well with Create React App console output.
You can use the default one instead if you prefer so.
const eslintFormatter = require('react-dev-utils/eslintFormatter');
// In your webpack config:
// ...
module: {
rules: [
{
test: /\.(js|jsx)$/,
include: paths.appSrc,
enforce: 'pre',
use: [
{
loader: 'eslint-loader',
options: {
// Pass the formatter:
formatter: eslintFormatter,
},
},
],
},
];
}Captures JS and CSS asset sizes inside the passed buildFolder. Save the result value to compare it after the build.
printFileSizesAfterBuild(webpackStats: WebpackStats, previousFileSizes: OpaqueFileSizes, buildFolder: string, maxBundleGzipSize?: number, maxChunkGzipSize?: number)
Prints the JS and CSS asset sizes after the build, and includes a size comparison with previousFileSizes that were captured earlier using measureFileSizesBeforeBuild(). maxBundleGzipSize and maxChunkGzipSizemay may optionally be specified to display a warning when the main bundle or a chunk exceeds the specified size (in bytes).
var {
measureFileSizesBeforeBuild,
printFileSizesAfterBuild,
} = require('react-dev-utils/FileSizeReporter');
measureFileSizesBeforeBuild(buildFolder).then(previousFileSizes => {
return cleanAndRebuild().then(webpackStats => {
printFileSizesAfterBuild(webpackStats, previousFileSizes, buildFolder);
});
});formatWebpackMessages({errors: Array<string>, warnings: Array<string>}): {errors: Array<string>, warnings: Array<string>}
Extracts and prettifies warning and error messages from webpack stats object.
var webpack = require('webpack');
var config = require('../config/webpack.config.dev');
var formatWebpackMessages = require('react-dev-utils/formatWebpackMessages');
var compiler = webpack(config);
compiler.hooks.invalid.tap('invalid', function() {
console.log('Compiling...');
});
compiler.hooks.done.tap('done', function(stats) {
var rawMessages = stats.toJson({}, true);
var messages = formatWebpackMessages(rawMessages);
if (!messages.errors.length && !messages.warnings.length) {
console.log('Compiled successfully!');
}
if (messages.errors.length) {
console.log('Failed to compile.');
messages.errors.forEach(e => console.log(e));
return;
}
if (messages.warnings.length) {
console.log('Compiled with warnings.');
messages.warnings.forEach(w => console.log(w));
}
});Prettify some known build errors. Pass an Error object to log a prettified error message in the console.
const printBuildError = require('react-dev-utils/printBuildError')
try {
build()
} catch(e) {
printBuildError(e) // logs prettified message
}
Finds the currently running process on port.
Returns a string containing the name and directory, e.g.,
create-react-app
in /Users/developer/create-react-app
var getProcessForPort = require('react-dev-utils/getProcessForPort');
getProcessForPort(3000);On macOS, tries to find a known running editor process and opens the file in it. It can also be explicitly configured by REACT_EDITOR, VISUAL, or EDITOR environment variables. For example, you can put REACT_EDITOR=atom in your .env.local file, and Create React App will respect that.
Returns Express middleware that serves a /service-worker.js that resets any previously set service worker configuration. Useful for development.
Attempts to open the browser with a given URL.
On Mac OS X, attempts to reuse an existing Chrome tab via AppleScript.
Otherwise, falls back to opn behavior.
var path = require('path');
var openBrowser = require('react-dev-utils/openBrowser');
if (openBrowser('http://localhost:3000')) {
console.log('The browser tab has been opened!');
}printHostingInstructions(appPackage: Object, publicUrl: string, publicPath: string, buildFolder: string, useYarn: boolean): void
Prints hosting instructions after the project is built.
Pass your parsed package.json object as appPackage, your the URL where you plan to host the app as publicUrl, output.publicPath from your Webpack configuration as publicPath, the buildFolder name, and whether to useYarn in instructions.
const appPackage = require(paths.appPackageJson);
const publicUrl = paths.publicUrl;
const publicPath = config.output.publicPath;
printHostingInstructions(appPackage, publicUrl, publicPath, 'build', true);Returns a Promise resolving to either defaultPort or next available port if the user confirms it is okay to do. If the port is taken and the user has refused to use another port, or if the terminal is not interactive and can’t present user with the choice, resolves to null.
Creates a Webpack compiler instance for WebpackDevServer with built-in helpful messages.
The args object accepts a number of properties:
- appName
string: The name that will be printed to the terminal. - config
Object: The webpack configuration options to be provided to the webpack constructor. - devSocket
Object: Required ifuseTypeScriptistrue. This object should includeerrorsandwarningswhich are functions accepting an array of errors or warnings emitted by the type checking. This is useful when runningfork-ts-checker-webpack-pluginwithasync: trueto report errors that are emitted after the webpack build is complete. - urls
Object: To provide theurlsargument, useprepareUrls()described below. - useYarn
boolean: Iftrue, yarn instructions will be emitted in the terminal instead of npm. - useTypeScript
boolean: Iftrue, TypeScript type checking will be enabled. Be sure to provide thedevSocketargument above if this is set totrue. - tscCompileOnError
boolean: Iftrue, errors in TypeScript type checking will not prevent start script from running app, and will not cause build script to exit unsuccessfully. Also downgrades all TypeScript type checking error messages to warning messages. - webpack
function: A reference to the webpack constructor.
Creates a WebpackDevServer proxy configuration object from the proxy setting in package.json.
Returns an object with local and remote URLs for the development server. Pass this object to createCompiler() described above.
This is an alternative client for WebpackDevServer that shows a syntax error overlay.
It currently supports only Webpack 3.x.
// Webpack development config
module.exports = {
// ...
entry: [
// You can replace the line below with these two lines if you prefer the
// stock client:
// require.resolve('webpack-dev-server/client') + '?/',
// require.resolve('webpack/hot/dev-server'),
'react-dev-utils/webpackHotDevClient',
'src/index',
],
// ...
};getCSSModuleLocalIdent(context: Object, localIdentName: String, localName: String, options: Object): string
Creates a class name for CSS Modules that uses either the filename or folder name if named index.module.css.
For MyFolder/MyComponent.module.css and class MyClass the output will be MyComponent.module_MyClass__[hash]
For MyFolder/index.module.css and class MyClass the output will be MyFolder_MyClass__[hash]
const getCSSModuleLocalIdent = require('react-dev-utils/getCSSModuleLocalIdent');
// In your webpack config:
// ...
module: {
rules: [
{
test: /\.module\.css$/,
use: [
require.resolve('style-loader'),
{
loader: require.resolve('css-loader'),
options: {
importLoaders: 1,
modules: {
getLocalIdent: getCSSModuleLocalIdent,
},
},
},
{
loader: require.resolve('postcss-loader'),
options: postCSSLoaderOptions,
},
],
},
];
}Returns a cache identifier (string) consisting of the specified environment and related package versions, e.g.,
var getCacheIdentifier = require('react-dev-utils/getCacheIdentifier');
getCacheIdentifier('prod', ['react-dev-utils', 'chalk']); // # => 'prod:react-dev-utils@5.0.0:chalk@3.0.0'