rollup.JS and "'this' keyword is equivalent to 'undefined' : <p>I'm trying to bundle Angular2 modules using Rollup.js.
this is my rollup.config.vendor.js file:</p>

<pre><code>import typescript from 'rollup-plugin-typescript2';
import resolve from 'rollup-plugin-node-resolve';
import commonjs from 'rollup-plugin-commonjs';

export default {
    entry: 'vendor.ts',
    dest: './Bundle/vendor.js',
    format: 'iife',
    moduleName: 'vendor',
    plugins: [
        typescript(),
        resolve({
            jsnext: true,
            main: true,
            browser: true
        }),
        commonjs({
            include: 'node_modules/rxjs/**',
        }),
    ]
}
</code></pre>

<p>It creates a bundled js, but in the process it keeps printing this kind of message:</p>

<pre><code>The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
https://github.com/rollup/rollup/wiki/Troubleshooting#this-is-undefined
node_modules\@angular\forms\@angular\forms.es5.js (1:25)
1: var __extends = (this &amp;&amp; this.__extends) || function (d, b) {
                            ^
2:     for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
3:     function __() { this.constructor = d; }
</code></pre>

<p>What does it mean?<br>
Am I doing something wrong or is it the way it's supposed to be?</p>
