为Promise添加finally方法支持，把小程序函数变成pr

// 为Promise添加finally方法支持
Promise.prototype.finally = function (callback) {
  let P = this.constructor;
  return this.then(
    value => P.resolve(callback()).then(() => value),
    reason => P.resolve(callback()).then(() => {
      throw reason
    })
  );
};

// 把小程序函数变成promise函数
const promisify = (fn) => {
  return (options, ...params) => {
    return new Promise((resolve, reject) => {
      fn(Object.assign({}, options, {
        success: resolve,
        fail: reject
      }), ...params);
    });
  }
};