ES3 compatible Object.assign

Object.assign.js

if (!('assign' in Object)) {
  Object.assign = function(has){
    'use strict';
    return assign;
    function assign(target, source) {
      for (var i = 1; i < arguments.length; i++) {
        copy(target, arguments[i]);
      }
      return target;
    }
    function copy(target, source) {
      for (var key in source) {
        if (has.call(source, key)) {
          target[key] = source[key];
        }
      }
    }
  }({}.hasOwnProperty);
}