text: /**
   * 泛型
   */
  function createArray(length, value) {
      var result = [];
      for (var i = 0; i < length; i++) {
          result[i] = value;
      }
      ;
      return result;
  }
  ;
  createArray(3, 'x');
  createArray(3, 2);
  function loggingIdentity(arg) {
      console.log(arg.length);
      return arg;
  }
  loggingIdentity('aaa');
  