Getting Error: Object doesn't support property or method 'assign'

As others have mentioned, the Object.assign() method is not supported in IE, but there is a polyfill available, just include it "before" your plugin declaration:

if (typeof Object.assign != 'function') {  Object.assign = function(target) {    'use strict';    if (target == null) {      throw new TypeError('Cannot convert undefined or null to object');    }    target = Object(target);    for (var index = 1; index < arguments.length; index++) {      var source = arguments[index];      if (source != null) {        for (var key in source) {          if (Object.prototype.hasOwnProperty.call(source, key)) {            target[key] = source[key];          }        }      }    }    return target;  };}

From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign

Test page: http://jsbin.com/pimixel/edit?html,js,output (just remove the polyfill to get the same error you're getting on your page).

@John Doe

I figured out from your comment that you want to implement this in node/react stack. This is very different from original question and you should have asked your own ;)
Anyways, Heres what you need to do...

You can use [es6-object-assign][1]. It is an ES6 Object.assign() "polyfill".

First, in package.json in your root folder, add es6-object-assign as a dependency:

"dependencies": {    "es6-object-assign": "^1.0.2",    "react": "^0.12.0",    ...  },

Then if you want to use it in node environment use:

require('es6-object-assign').polyfill();

If you are having the issue on front (browser) end...
Add it in your index.html file...

<script src="location_of_node_modules/es6-object-assign/dist/object-assign.min.js"></script><script>  window.ObjectAssign.polyfill();</script>

location_of_node_modules depends on boilerplate you use, mostly just node_modules, but sometimes when index.html is in a subdirectory you need to use, ../node_modules

As per the documentation, Object.assign() is a new technology, part of the ECMAScript 2015 (ES6) standard:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign

And it is not supported by IE.