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rollup-plugin-legacy

Add export declarations to legacy non-module scripts.

Installation

npm install --save-dev rollup-plugin-legacy

Motivation

Occasionally you'll find a useful snippet of code from the Old Days, before newfangled technology like npm. These scripts will typically expose themselves as var someLibrary = ... or window.someLibrary = ..., the expectation being that other scripts will grab a reference to the library from the global namespace.

It's usually easy enough to convert these to modules. But why bother? You can just add the legacy plugin, configure it accordingly, and it will be turned into a module automatically. With the example config below, the following code...

// vendor/some-library.js
var someLibrary = {
  square: function(n) {
    return n * n;
  },
  cube: function(n) {
    return n * n * n;
  }
};

...will have a default export appended to it, allowing other modules to access it:

export default someLibrary;

It can also handle named exports. Using the same config, this...

// vendor/another-library.js
var anotherLibrary = {
  foo: ...,
  bar: ...,
  baz: ...
};

...will get the following appended:

var __export0 = anotherLibrary.foo; export { __export0 as foo };
var __export0 = anotherLibrary.bar; export { __export0 as bar };
var __export0 = anotherLibrary.baz; export { __export0 as baz };

Usage

// rollup.config.js
import legacy from 'rollup-plugin-legacy';

export default {
  entry: 'src/main.js',
  dest: 'bundle.js',
  format: 'iife',
  plugins: [
    legacy({
      // add a default export, corresponding to `someLibrary`
      'vendor/some-library.js': 'someLibrary',

      // add named exports
      'vendor/another-library.js': {
        foo: 'anotherLib.foo',
        bar: 'anotherLib.bar',
        baz: 'anotherLib.baz'
      }
    })
  ]
}

License

MIT