Add support Object.assign old browsers. Source: http://codepen.io/souporserious/pen/Boavdv

object_assign.js

/* Add suspport assign method (> IE9)
*  https://gist.github.com/icetee/fae755b7ce8f90d9d7bc8a7ece2cf3cb
*/
if (!Object.assign && Object.hasOwnProperty('defineProperty')) {
  Object.defineProperty(Object, 'assign', {
    enumerable: false,
    configurable: true,
    writable: true,
    value: function(target) {
      'use strict';
      if (target === undefined || target === null) {
        throw new TypeError('Cannot convert first argument to object');
      }

      var to = Object(target);
      for (var i = 1; i < arguments.length; i++) {
        var nextSource = arguments[i];
        if (nextSource === undefined || nextSource === null) {
          continue;
        }
        nextSource = Object(nextSource);

        var keysArray = Object.keys(Object(nextSource));
        for (var nextIndex = 0, len = keysArray.length; nextIndex < len; nextIndex++) {
          var nextKey = keysArray[nextIndex];
          var desc = Object.getOwnPropertyDescriptor(nextSource, nextKey);
          if (desc !== undefined && desc.enumerable) {
            to[nextKey] = nextSource[nextKey];
          }
        }
      }
      return to;
    }
  });
}

object_assign.min.js

/* Add suspport assign method (> IE9)
*  https://gist.github.com/icetee/fae755b7ce8f90d9d7bc8a7ece2cf3cb
*/
if(!Object.assign&&Object.hasOwnProperty("defineProperty")){Object.defineProperty(Object,"assign",{enumerable:false,configurable:true,writable:true,value:function(g){if(g===undefined||g===null){throw new TypeError("Cannot convert first argument to object")}var j=Object(g);for(var a=1;a<arguments.length;a++){var d=arguments[a];if(d===undefined||d===null){continue}d=Object(d);var b=Object.keys(Object(d));for(var c=0,f=b.length;c<f;c++){var h=b[c];var e=Object.getOwnPropertyDescriptor(d,h);if(e!==undefined&&e.enumerable){j[h]=d[h]}}}return j}})};