创建create-react-app全家桶并添加less配置

1. npx create-react-app my-app

2. cd my-app
3. npm start     //运行该项目

create-react-app生成的项目文，看不到webpack相关的配置文件，需要先暴露出来，使用如下命令即可

4. npm run eject   //yes  

5. npm install less-loader less --save-dev    //如果之前已经全局安装过less了，去掉`-dev`即可

修改 webpack.config.dev.js 和 webpack.config-prod.js 配置文件

exclude: [
  /\.html$/,
  /\.(js|jsx)$/,
  /\.(css|less)$/,   //敲黑板，划重点
  /\.json$/,
  /\.bmp$/,
  /\.gif$/,
  /\.jpe?g$/,
  /\.png$/,
],
{
  test: /\.(css|less)$/,   //敲黑板，划重点
  use: [
    require.resolve('style-loader'),
    {
      loader: require.resolve('css-loader'),
      options: {
        importLoaders: 1,
      },
    },
    {
      loader: require.resolve('postcss-loader'),
      options: {
        // Necessary for external CSS imports to work
        // https://github.com/facebookincubator/create-react-app/issues/2677
        ident: 'postcss',
        plugins: () => [
          require('postcss-flexbugs-fixes'),
          autoprefixer({
            browsers: [
              '>1%',
              'last 4 versions',
              'Firefox ESR',
              'not ie < 9', // React doesn't support IE8 anyway
            ],
            flexbox: 'no-2009',
          }),
        ],
      },
    },
    //敲黑板，划重点
    {
      loader: require.resolve('less-loader') // compiles Less to CSS
    }
  ],
}

.在项目中安装 Babel 转换器，需要用到插件 babel-preset-react, babel-preset-latest，latest 即最新的 ES 规范，包括了 Async/Await 这些新特性

6. npm install babel-loader babel-core babel-preset-react babel-preset-latest --save