Promise 的一些扩展方法

// promise.done()
Promise.prototype.done = function (onFulfilled, onRejected) {
  this.then(onFulfilled, onRejected).catch(function (reason) {
    // 抛出一个全局错误
    setTimeout(() => {
      throw reason;
    }, 0);
  });
};

// promise.finally()
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;
      }),
  );
};

// promise.if()
Promise.prototype.if = function (flag, planAS, planBS) {
  return flag ? Promise.all(planAS.map((f) => f())) : Promise.all(planBS.map((f) => f()));
};