Webpack with babel-loader not emitting valid es5 - vue.js

Question

I have a webpack config that is based off https://github.com/vuejs-templates/webpack-simple/blob/master/template/webpack.config.js
It uses vue-loader and babel-loader. The issue is I cannot get it to generate ES5 code so that it will work in the most broad range of clients.
If I use the ES2015 preset, webpack.optimize.UglifyJsPlugin fails to minify the output because Uglify can only handle ES5 (not counting the harmony branch). The errors are similar to: Unexpected token: punc (() and occur in multiple files.
I can work around this by using babili-webpack-plugin which will minify the ES6 code but is very slow. However, when I deploy this code, I see errors being reported back saying Block-scoped declarations (let, const, function, class) not yet supported outside strict mode so I know they are older clients choking on ES6 code.
How can I get proper ES5 code output from babel-loader? I have tried multiple presets, with or without the transform-runtime plugin. Config below:
const webpack = require('webpack');
const globEntries = require('webpack-glob-entries');
const _ = require('lodash');
const path = require('path');
const BabiliPlugin = require("babili-webpack-plugin");
const env = process.env.NODE_ENV;
let entries;
if (env === 'production') {
entries = globEntries('./src/**/vue/*.js');
} else {
entries = _.mapValues(globEntries('./src/**/vue/*.js'), entry => [entry, 'webpack-hot-middleware/client?reload=true']);
}
module.exports = {
entry: entries,
output: {
path: '/', ///no real path is required, just pass "/"
publicPath: '/vue',
filename: '[name].js',
},
module: {
rules: [
{
test: /\.vue$/,
loader: 'vue-loader',
options: {
loaders: {
scss: 'vue-style-loader!css-loader!sass-loader',
sass: 'vue-style-loader!css-loader!sass-loader?indentedSyntax',
},
// other vue-loader options go here
},
},
{
test: /\.js$/,
exclude: /node_modules/,
use: {
loader: 'babel-loader',
query: {
presets: ['es2015'],
plugins: ['transform-runtime'],
},
},
},
{
test: /\.(png|jpg|gif|svg)$/,
loader: 'file-loader',
options: {
name: '[name].[ext]?[hash]',
},
},
],
},
resolve: {
alias: {
vue$: 'vue/dist/vue.esm.js',
},
},
plugins: [
new webpack.HotModuleReplacementPlugin(), // Enable HMR
new webpack.NoEmitOnErrorsPlugin(),
],
performance: {
hints: false,
},
devtool: '#eval-source-map',
};
if (env === 'staging' || env === 'production') {
//module.exports.devtool = env === 'staging' ? '#source-map' : false;
module.exports.devtool = '#source-map';
module.exports.output.path = path.resolve(__dirname, './src/v1/parse/cloud/public/vue');
// http://vue-loader.vuejs.org/en/workflow/production.html
module.exports.plugins = (module.exports.plugins || []).concat([
new webpack.DefinePlugin({
'process.env': {
NODE_ENV: `"${env}"`,
},
}),
new webpack.optimize.UglifyJsPlugin({
sourceMap: true,
compress: {
warnings: false,
},
}),
// new BabiliPlugin(),
new webpack.LoaderOptionsPlugin({
minimize: true,
}),
]);
}

Answer 1

vue-loader will process your js with babel-loader (if it's detected), and uses .babelrc by default.
In your current setup you are not passing any options to Babel when it is used by vue-loader (meaning Babel uses no rules for your Vue files).
Either create .babelrc or specify the js loader by yourself for the .vue files to provide it with options:
{
test: /\.vue$/,
loader: 'vue-loader',
options: {
loaders: {
js: 'babel?presets[]=es2015' // Pass parameters as options
}
}
}
The env preset for Babel has an uglify option that will fully compile to ES5. This preset is recommended practice to keep your environment up to date.
// .babelrc
{
"presets": [
[ "env", { "uglify": true } ],
"stage-1" // Or other presets not included with 'env' preset.
],
"plugins": ["transform-runtime"]
}
Instead of using preset es2015 only, you might add es2016 and es2017, as well as stage-4, stage-3, etc. to assure all your code is transformed, and not just the ES2015 parts.

Answer 2

Nothing wrong with answer here already, but here is a solution that does not require a .babelrc file. This answer works for a standalone webpack.config.js file. I got this answer from taking a look under the hood of the laravel-mix library.
module: {
rules: [
{
test: /\.js$/,
loader: 'babel-loader',
exclude: /node_modules/
},
{
test: /\.vue$/,
loader: 'vue-loader',
options: {
loaders:{
js: {
loader: 'babel-loader',
options: {
cacheDirectory: true,
presets: [
['env', {
'modules': false,
'targets': {
'browsers': ['> 2%'],
uglify: true
}
}]
],
plugins: [
'transform-object-rest-spread',
['transform-runtime', {
'polyfill': false,
'helpers': false
}]
]
}
},
}
}
},
{
test: /\.(png|jpg|gif|svg)$/,
loader: 'file-loader',
options: {
name: '[name].[ext]?[hash]'
}
}
]
},
I spent the better part of a day reading up all these useless blogs omit the core concept that babel-loader has to be attached to the vue-loader.