Webpack - provide core-js polyfills

Question

I need to create a bundle that has right on top of it the es6 polyfills so that methods like Object.assign, Array.prototype.filter and so on are backed by core-js in case they are not defined natively.

I've created a simple sample application that isolates this problem that I have and it is pushed to a gist here : https://gist.github.com/tiberiucorbu/fb9acd2f286e3452ef06df9d6bae9210

Now webpack is very confusing when it comes to polyfills, I've tried different approaches but nothing seems to work as I've imagined :

Using the provider plugin

Inspiration : https://webpack.github.io/docs/shimming-modules.html

Try :

webpack.config.js

    new webpack.ProvidePlugin({
        '': 'imports?this=>window!core-js/index.js'
    })

Result :

Nothing different happen. as If I didn't change anything. the bundle is the same without it. My small test fails :

PhantomJS 2.1.1 (Windows 7 0.0.0) Application extend should use Object.assign FAILED
        Failed: undefined is not a constructor (evaluating 'Object.assign(a, b)')
        [email protected]:81:30
        index.spec.ts:59:44
        loaded@http://localhost:9876/context.js:151:17

Define core-js files into the webpacks entry config:

Try :

entry: {
    'app': [
        'core-js',
        './index.ts'
    ]
},

Result : The bundle contains the core-js files but they are not ran. The spec continues to fail.

So how can I make sure that the bundle contains the polyfills and they are properly ran in this (webpack, karma, typescript) constellation ?

---

Update : (Somehow) working solution

I've tried another aproach using another mindset: import polyfills and execute polyfills while leting webpack/typescript to handle the imports and a script of mine to handle the execution. Feels a bit hackish but it works.

Changes from the initial posted version :

@@ -3,8 +3,10 @@ var webpack = require('webpack');
 module.exports = {
     entry: {
         'app': [
-            'core-js',
             './index.ts'
+        ],
+        'polyfills': [
+            'core-js'
         ]
     },
     output: {
@@ -30,4 +32,4 @@ module.exports = {
         //   '': 'imports?this=>window!core-js/index.js'
         // })
     ]
-};
\ No newline at end of file
+};

Created a new file that imports core-js as name and executes that name:

import * as polyfills from 'core-js';

polyfills();

and after that imported the bundle along the test files in the karma configuration:

@@ -4,6 +4,7 @@ module.exports = function (config) {
     config.set({
         frameworks: ['jasmine'],
         files: [
+            './dist/polyfills.js',
             './**/*.spec.ts'

         ],
@@ -26,4 +27,4 @@ module.exports = function (config) {
         concurrency: Infinity,
         plugins: ['karma-phantomjs-launcher', 'karma-sourcemap-loader', 'karma-webpack', 'karma-jasmine']
     })
-};
\ No newline at end of file
+};

My small test succeeds:

26 01 2017 01:30:40.594:INFO [karma]: Karma v1.3.0 server started at http://localhost:9876/
26 01 2017 01:30:40.596:INFO [launcher]: Launching browser PhantomJS with unlimited concurrency
26 01 2017 01:30:40.613:INFO [launcher]: Starting browser PhantomJS
26 01 2017 01:30:41.081:INFO [PhantomJS 2.1.1 (Linux 0.0.0)]: Connected on socket /#c9shUPdbgFg0XwJbAAAA with id 77560741
PhantomJS 2.1.1 (Linux 0.0.0): Executed 1 of 1 SUCCESS (0.04 secs / 0.002 secs)

The Gist is now on a working state with the changes mentioned above :

https://gist.github.com/tiberiucorbu/fb9acd2f286e3452ef06df9d6bae9210

If you know a more elegant solution without a middle file would be a nice to have/know, but at this point I can work with it as it is.

Answer 1

You can use a different approach, just letting webpack ensure the ES6 compatibility using babel:

webpack.config.js

module.exports = {
    ...
    module: { 
       loaders: [
          { 
              test: /\.jsx?$/, 
              loader: 'babel-loader', 
              exclude: /node_modules/, 
              query: { 
                 presets: ['es2015'] 
              }
          }
       ]
    }
} 

For install babel loader:

npm install babel-loader babel-core babel-preset-es2015 webpack --save-dev

Using babel, you can use all ES6 in its fully glory:

import $ from 'jquery'

const cool = w => 42

And no polyfills will be needed