Webpack not converting ES6 to ES5

问题:

I'm very new to Webpack. I think I'm doing it incorrectly. I would like to convert an ES6 function to ES5 function using babel. So I did some research and I found babel-loader. However, I'm not sure what I'm doing.

I ran npm install babel-loader --save-dev and it got added into my package.json

// package.json

{
  "name": "kanban",
  "version": "1.0.0",
  "description": "kanban",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-core": "^6.3.21",
    "babel-loader": "^6.2.0",
    "html-webpack-plugin": "^1.7.0",
    "json-loader": "^0.5.4",
    "webpack": "^1.12.9"
  }
}

// webpack.config.js

var path = require('path');
var HtmlwebpackPlugin =  require('html-webpack-plugin');

const PATHS = {
  app: path.join(__dirname, 'app'),
  build: path.join(__dirname, 'build')
};

module.exports = {
  entry: PATHS.app,
  output: {
    path: PATHS.build,
    filename: 'bundle.js'
  },
  plugins: [
    new HtmlwebpackPlugin({
      title: 'Kanban app'
    })
  ],
  module: {
    loaders: [
      { test: /\.js$/, loader: 'babel-loader' }
    ]
  }
};

// app/index.js - I just added some random useless function in ES6 syntax. I was hoping I'll see the ES5 format in my bundle.js file but it didn't change. It's still ES6 syntax in bundle.js

var component = require('./component');
var app = document.createElement('div');
document.body.appendChild('app');
app.appendChild(component());

let myJson = {
  prop: 'myProp'
};

let fives = [];
nums = [1, 2, 5, 15, 25, 32];

// Statement bodies
nums.forEach(function (v) {
  if (v % 5 === 0) {
    fives.push(v);
  }
}, this);

console.log(fives);

let sum = (a, b) => a + b; 

// app/component.js

module.exports = function() {
  var element = document.createElement('h1');
  element.innerHTML = 'hello world';
  return element;
};

回答1:

If you want to compile ES6 to ES5 you need to install Babel ES2015 preset.

npm install babel-preset-es2015

Then you need to enable this preset. One way to enable this ES6 to ES5 compilation is using babel-loader query string:

  module: {
    loaders: [
      {
        test: /\.js$/,
        loader: 'babel-loader?presets[]=es2015'
      }
    ]
  }

or query option:

  module: {
    loaders: [
      {
        test: /\.js$/,
        loader: 'babel-loader',
        query: {
          presets: ['es2015']
        }
      }
    ]
  }

回答2:

for webpack 3, the module options should look like

module: {
  rules: [
    {
       use: {
          loader:'babel-loader',
          options: { presets: ['es2015'] }
       },
       test: /\.js$/,
       exclude: /node_modules/
    }
  ]
},

this still requires babel-loader and babel-preset-es2015

回答3:

I got the same problem. Well, official react answer to add this configurations to webpack

{
  "presets": ["es2015", "react", "stage-0"],
  "plugins": ["react-hot-loader/babel"]
}

here is the link: https://github.com/facebook/react/issues/8379