React-greate-app/react-script如何找到入口点

Question

在本教程中， npm start如何找到 src/index/js饰演渲染？我找不到任何地方的配置。

Answer 1

您可以运行npm run eject，以便该项目回到普通的WebPack项目。然后，您可以找到配置。

Answer 2

如果查看package.json，则在此处定义start脚本：

"scripts": {
  "start": "react-scripts start",

它运行react-scripts start。和react-scripts的package.json文件看起来像：

"bin": {
    "react-scripts": "./bin/react-scripts.js"
  },

因此，我们应该看到./bin/react-scripts.js start的操作，它运行此代码：

// @remove-on-eject-begin
/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
// @remove-on-eject-end
'use strict';
// 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('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');
const openBrowser = require('react-dev-utils/openBrowser');
const semver = require('semver');
const paths = require('../config/paths');
const configFactory = require('../config/webpack.config');
const createDevServerConfig = require('../config/webpackDevServer.config');
const getClientEnvironment = require('../config/env');
const react = require(require.resolve('react', { paths: [paths.appPath] }));
const env = getClientEnvironment(paths.publicUrlOrPath.slice(0, -1));
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://cra.link/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,
      paths.publicUrlOrPath.slice(0, -1)
    );
    // Create a webpack compiler that is configured with custom messages.
    const compiler = createCompiler({
      appName,
      config,
      urls,
      useYarn,
      useTypeScript,
      webpack,
    });
    // Load proxy config
    const proxySetting = require(paths.appPackageJson).proxy;
    const proxyConfig = prepareProxy(
      proxySetting,
      paths.appPublic,
      paths.publicUrlOrPath
    );
    // Serve webpack assets generated by the compiler over a web server.
    const serverConfig = {
      ...createDevServerConfig(proxyConfig, urls.lanUrlForConfig),
      host: HOST,
      port,
    };
    const devServer = new WebpackDevServer(serverConfig, compiler);
    // Launch WebpackDevServer.
    devServer.startCallback(() => {
      if (isInteractive) {
        clearConsole();
      }
      if (env.raw.FAST_REFRESH && semver.lt(react.version, '16.10.0')) {
        console.log(
          chalk.yellow(
            `Fast Refresh requires React 16.10 or higher. You are using React ${react.version}.`
          )
        );
      }
      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();
      });
    });
    if (process.env.CI !== 'true') {
      // Gracefully exit when stdin ends
      process.stdin.on('end', function () {
        devServer.close();
        process.exit();
      });
    }
  })
  .catch(err => {
    if (err && err.message) {
      console.log(err.message);
    }
    process.exit(1);
  });

启动WebPack服务器的

：

 const devServer = new WebpackDevServer(serverConfig, compiler);
    // Launch WebpackDevServer.
    devServer.startCallback(() => {

然后打开浏览器：

openBrowser(urls.localUrlForBrowser);

Answer 3

在运行NPM运行弹射时，您可以找到带有所有配置文件的配置文件夹。在path.js文件内部，您可以找到默认路径，如果需要，您可以更改那里的默认路径。这样做时要小心，因为这是一个不可逆转的过程

ref：http：//blog.teamtreehouse.com/getting-started-create-react-app-tool