code: function createPromise(resolver) {
          return {
              'then': function (onFulfilled, onRejected) {
                  return then(resolver, onFulfilled, onRejected);
              },
  
              'catch': function (onRejected) {
                  return then(resolver, null, onRejected);
              }
          };
      }
docs: 创建Promise对象
  
  @inner
  @param {Resolver} resolver resolver对象
  @return {Object}