Babel es2015预设不会将Map和Set转换为es5

Question

I'm using gulp-babel to translate my es6 code to es5

gulp.task('build_all_debug', ['config', 'compile'], function() {
    var stream = gulp.src(['public/js/config.js', 'public/js/*.js', 'public/compiled/*.js'])
        .pipe(babel({
            presets: ['es2015']
        }))
        .pipe(concat('app.js'))
        .pipe(gulp.dest('public/dist'));
    return stream;
});

While it mostly works fine, it doesn't actually translate Map and Set. My result js code still includes them, and when I run unit test with karma/mocha/phantomJs, I got the following error:

PhantomJS 2.1.1 (Mac OS X 0.0.0) notes.controller "before each" hook: workFn for "loads notes from the service" FAILED
    Can't find variable: Map
    activate@public/dist/app.js:2402:39

Is there any way to force babel to translate Map and Set to object and array in es5?

Answer 1

You have to include babel-polyfill in your code.

You have to install it with npm:

npm install babel-polyfill

and then, if you're using ES6 modules:

import 'babel-polyfill';

or:

require('babel-polyfill');

If you want to run your code in browser, you can load it from cdnjs:

<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-polyfill/6.16.0/polyfill.min.js"></script>

Answer 2

Babel can't "translate" Map and Set , because they aren't language features (although they are described in the ES spec). They're classes that exist in the global scope.

You should use a polyfill that defines the ES6 collections, so you can keep using them in browsers that don't provide support. I'm not sure what library Babel uses, but es6-shim should cover all the major parts.

You won't need to change your code any to use the polyfill, it just defines Map (and friends) for normal use later.

Answer 3

Babel does not transpile Map and Set to ES5.

Instead, use their polyfill :

In order to support Maps, Sets, WeakMaps, and WeakSets in all environments you must include the Babel polyfill.

Source