scripts/start.js
// Do this as the first thing so that any code reading it knows the right env.
process.env.BABEL_ENV = 'development'
process.env.NODE_ENV = 'development'
// Makes the script crash on unhandled rejections instead of silently
// ignoring them. In the future, promise rejections that are not handled will
// terminate the Node.js process with a non-zero exit code.
process.on('unhandledRejection', (err) => {
throw err
})
// Ensure environment variables are read.
require('./config/env')
const fs = require('fs')
const chalk = require('chalk')
const webpack = require('webpack')
const { checkBrowsers } = require('react-dev-utils/browsersHelper')
const WebpackDevServer = require('webpack-dev-server')
const clearConsole = require('react-dev-utils/clearConsole')
const checkRequiredFiles = require('react-dev-utils/checkRequiredFiles')
const {
choosePort,
createCompiler,
prepareProxy,
prepareUrls,
} = require('react-dev-utils/WebpackDevServerUtils')
const openBrowser = require('react-dev-utils/openBrowser')
const paths = require('./config/paths')
const config = require('./config/webpack.config.dev')
const createDevServerConfig = require('./config/webpackDevServer.config')
const useYarn = fs.existsSync(paths.yarnLockFile)
const isInteractive = process.stdout.isTTY
// Warn and crash if required files are missing
if (!checkRequiredFiles([paths.appHtml, paths.appIndexJs])) {
process.exit(1)
}
// Tools like Cloud9 rely on this.
const DEFAULT_PORT = parseInt(process.env.PORT, 10) || 3000
const HOST = process.env.HOST || '0.0.0.0'
if (process.env.HOST) {
console.info(
chalk.cyan(
`Attempting to bind to HOST environment variable: ${chalk.yellow(
chalk.bold(process.env.HOST),
)}`,
),
)
console.info(
"If this was unintentional, check that you haven't mistakenly set it in your shell.",
)
console.info(
`Learn more here: ${chalk.yellow('http://bit.ly/CRA-advanced-config')}`,
)
console.info()
}
// We require that you explictly set browsers and do not fall back to
// browserslist defaults.
checkBrowsers(paths.appPath, isInteractive)
.then(() => choosePort(HOST, DEFAULT_PORT))
.then((port) => {
if (port == null) {
// We have not found a port.
return
}
const protocol = process.env.HTTPS === 'true' ? 'https' : 'http'
const appName = require(paths.appPackageJson).name
const urls = prepareUrls(protocol, HOST, port)
// Create a webpack compiler that is configured with custom messages.
const compiler = createCompiler(webpack, config, appName, urls, useYarn)
// Load proxy config
const proxySetting = require(paths.appPackageJson).proxy
const proxyConfig = prepareProxy(proxySetting, paths.appPublic)
// Serve webpack assets generated by the compiler over a web server.
const serverConfig = createDevServerConfig(
proxyConfig,
urls.lanUrlForConfig,
)
const devServer = new WebpackDevServer(compiler, serverConfig)
// Launch WebpackDevServer.
devServer.listen(port, HOST, (err) => {
if (err) {
return console.info(err)
}
if (isInteractive) {
clearConsole()
}
console.info(chalk.cyan('Starting the development server...\n'))
openBrowser(urls.localUrlForBrowser)
})
;['SIGINT', 'SIGTERM'].forEach((sig) => {
process.on(sig, () => {
devServer.close()
process.exit()
})
})
})
.catch((err) => {
if (err && err.message) {
console.info(err.message)
}
process.exit(1)
})