菜鸟学习 react 中，配置文件有点乱，研究一波。
yarn eject 之后，文件目录相比之前只是多了 config 和 scripts 两个文件夹，package.json 多了很多配置项, 所以本文主要解决 config 和 package.json 两个部分.
一.config 文件夹下，还有一个 jest 文件夹是 jest 测试文件，cssTransform.js 和 fileTransform.js 对应 package.json 中的
"transform": {"^.+\\.(js|jsx|ts|tsx)$": "<rootDir>/node_modules/babel-jest",
"^.+\\.css$": "<rootDir>/config/jest/cssTransform.js",
"^(?!.*\\.(js|jsx|ts|tsx|css|json)$)": "<rootDir>/config/jest/fileTransform.js"
},二. 重点分析，从 package.json 命令行入手，
"scripts": {
"start": "node scripts/start.js",
"build": "node scripts/build.js",
"test": "node scripts/test.js"
},看命令就知道 scripts 下的三个文件，分别对应开发，打包和测试三个环境的入口。
config/path.js 里面路径变量
const resolveApp = relativePath => path.resolve(appDirectory, relativePath);// 解析对应文件的绝对路径
const getPublicUrl = appPackageJson =>
envPublicUrl || require(appPackageJson).homepage;// 赋值下面变量 publicUrl，从 env.js 或者 package.json 中获取 homepage
function getServedPath(appPackageJson) {const publicUrl = getPublicUrl(appPackageJson);
const servedUrl =
envPublicUrl || (publicUrl ? url.parse(publicUrl).pathname : '/');
return ensureSlash(servedUrl, true);
}// 服务域名
----------
dotenv: resolveApp('.env'),
appPath: resolveApp('.'),
appBuild: resolveApp('build'),
appPublic: resolveApp('public'),
appHtml: resolveApp('public/index.html'),
appIndexJs: resolveModule(resolveApp, 'src/index'),
appPackageJson: resolveApp('package.json'),
appSrc: resolveApp('src'),
appTsConfig: resolveApp('tsconfig.json'),
appJsConfig: resolveApp('jsconfig.json'),
yarnLockFile: resolveApp('yarn.lock'),
testsSetup: resolveModule(resolveApp, 'src/setupTests'),
proxySetup: resolveApp('src/setupProxy.js'),
appNodeModules: resolveApp('node_modules'),
publicUrl: getPublicUrl(resolveApp('package.json')),
servedPath: getServedPath(resolveApp('package.json')),1.start.js 其实就是开发环境 devserver 的配置和启动
process.env.BABEL_ENV = 'development';//bebel 用到环境变量 (@babel/preset-react)
process.env.NODE_ENV = 'development';// 全局 node 环境变量
process.on('unhandledRejection', err => {throw err;});
// Ensure environment variables are read.
require('../config/env');// 开发环境配置文件
const fs = require('fs');
const chalk = require('react-dev-utils/chalk');
const webpack = require('webpack');
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');
----------
//TODO 下面就是对应 devserver 的详细配置了，open,host,port,http,proxy 等，都是从对应的文件中读取，env.js，package.json 等
const openBrowser = require('react-dev-utils/openBrowser');
const paths = require('../config/paths');
const configFactory = require('../config/webpack.config');//webpack 对应环境配置的函数
const createDevServerConfig = require('../config/webpackDevServer.config');
//devserver 的配置文件
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.log(
chalk.cyan(
`Attempting to bind to HOST environment variable: ${chalk.yellow(chalk.bold(process.env.HOST)
)}`
)
);
console.log(`If this was unintentional, check that you haven't mistakenly set it in your shell.`);
console.log(`Learn more here: ${chalk.yellow('https://bit.ly/CRA-advanced-config')}`
);
console.log();}
// We require that you explicitly set browsers and do not fall back to
// browserslist defaults.
const {checkBrowsers} = require('react-dev-utils/browsersHelper');
checkBrowsers(paths.appPath, isInteractive)
.then(() => {
// We attempt to use the default port but if it is busy, we offer the user to
// run on a different port. `choosePort()` Promise resolves to the next free port.
return choosePort(HOST, DEFAULT_PORT);
})
.then(port => {if (port == null) {
// We have not found a port.
return;
}
const config = configFactory('development');
const protocol = process.env.HTTPS === 'true' ? 'https' : 'http';
const appName = require(paths.appPackageJson).name;
const useTypeScript = fs.existsSync(paths.appTsConfig);
const urls = prepareUrls(protocol, HOST, port);
const devSocket = {
warnings: warnings =>
devServer.sockWrite(devServer.sockets, 'warnings', warnings),
errors: errors =>
devServer.sockWrite(devServer.sockets, 'errors', errors),
};
// Create a webpack compiler that is configured with custom messages.
const compiler = createCompiler({
appName,
config,
devSocket,
urls,
useYarn,
useTypeScript,
webpack,
});
// 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
);
----------
//TODO devserver 开发服务启动
const devServer = new WebpackDevServer(compiler, serverConfig);
// Launch WebpackDevServer.
devServer.listen(port, HOST, err => {if (err) {return console.log(err);
}
if (isInteractive) {clearConsole();
}
// We used to support resolving modules according to `NODE_PATH`.
// This now has been deprecated in favor of jsconfig/tsconfig.json
// This lets you use absolute paths in imports inside large monorepos:
if (process.env.NODE_PATH) {
console.log(
chalk.yellow('Setting NODE_PATH to resolve modules absolutely has been deprecated in favor of setting baseUrl in jsconfig.json (or tsconfig.json if you are using TypeScript) and will be removed in a future major release of create-react-app.'
)
);
console.log();}
console.log(chalk.cyan('Starting the development server...\n'));
openBrowser(urls.localUrlForBrowser);
});
['SIGINT', 'SIGTERM'].forEach(function(sig) {process.on(sig, function() {devServer.close();
process.exit();});
});
})
.catch(err => {if (err && err.message) {console.log(err.message);
}
process.exit(1);
});