Object.assign() browser polyfill

object-assign.js

if (!Object.assign) {
  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;
    }
  });
}

thx

This sets the wrong values for Object.assign.name (it will get set to value instead of assign) and Object.assign.length (it will get set to 1 instead of 2).

I recommend the following approach instead, which has the additional advantage being more readable:

if (!Object.assign) {
  Object.assign = function assign(target, source) {
    /* implementation omitted */
  };
  Object.defineProperty(Object, 'assign', {enumerable: false});
}