code: function objectKeys(obj) {
    if (!obj) { return null; }
  
    if (Object.keys) {
      return Object.keys(obj);
    }
  
    var out = [];
  
    for (var key in obj) {
      if (obj.hasOwnProperty(key)) {
        out.push(key);
      }
    }
  
    return out;
  }
docs: Get the keys of an object.
  @param {object} obj The object.
  @return {array} An array of keys.