1.使用 create-react-app 创建的项目，默认情况下是看不到 webpack 相关的配置文件，我们需要给它暴露出来，使用下面命令即可：
npm run eject
2.添加less
npm install less less-loader --save-dev
3.修改webpack配置文件 （修改下面两段代码即可）
const cssRegex = /\.(css|less)$/;
const getStyleLoaders = (cssOptions, preProcessor) => {
const loaders = [
isEnvDevelopment && require.resolve('style-loader'),
isEnvProduction && {
loader: MiniCssExtractPlugin.loader,
options: shouldUseRelativeAssetPaths ? { publicPath: '../../' } : {},
},
{
loader: require.resolve('css-loader'),
options: cssOptions,
},
{
loader: require.resolve('less-loader'),// compiles Less to CSS
options: cssOptions,
},
{
// Options for PostCSS as we reference these options twice
// Adds vendor prefixing based on your specified browser support in
// package.json
loader: require.resolve('postcss-loader'),
options: {
// Necessary for external CSS imports to work
// https://github.com/facebook/create-react-app/issues/2677
ident: 'postcss',
plugins: () => [
require('postcss-flexbugs-fixes'),
require('postcss-preset-env')({
autoprefixer: {
flexbox: 'no-2009',
},
stage: 3,
}),
// Adds PostCSS Normalize as the reset css with default options,
// so that it honors browserslist config in package.json
// which in turn let's users customize the target behavior as per their needs.
postcssNormalize(),
],
sourceMap: isEnvProduction && shouldUseSourceMap,
},
},
].filter(Boolean);
if (preProcessor) {
loaders.push(
{
loader: require.resolve('resolve-url-loader'),
options: {
sourceMap: isEnvProduction && shouldUseSourceMap,
},
},
{
loader: require.resolve(preProcessor),
options: {
sourceMap: true,
},
}
);
}
return loaders;
};