實現webpack的babel-loader

實現babel-loader

babel-loader:

let babel = require('@babel/core');
 let loaderUtils = require('loader-utils');
 function loader(source) {   // this loaderContext
     let options = loaderUtils.getOptions(this);
     let cb = this.async();
     babel.transform(source, {
         ...options,
         sourceMap: true,
         filename: this.resourcePath.split('/').pop(),
     }, function (err, result) {
         cb(err, result.code, result.map);
     });
 }
 
 module.exports = loader;

webpack.config.js

let path= require('path');

module.exports = {
    entry: './src/index.js',
    output: {
        filename: 'index.js',
        path: path.resolve(__dirname, 'dist')
    },
    mode: 'development',
    resolveLoader: {
        modules: ['node_modules', path.resolve(__dirname, 'loaders')],
    },
    devtool: "source-map",
    module: {
        // loader的分類，pre在前面的， post在後面， 然後就是普通normal
        // loader的順序  pre +normal + inline + post;   從右向左，從下倒上
        rules: [
            {
                test: /\.js$/,
                use: {
                    loader: 'babel-loader',
                    options: {
                        presets: [
                            '@babel/preset-env'
                        ]
                    }
                }
            }
        ]
    }
};