Promise 的取消

有时候需要取消Promise

 

const CancelEerr = "CANCEL"

class CancelPromise {
  constructor(fun,/* 后续的任务都取消 */isDeep = false) {
    this.prom = new Promise(fun)

    this._cancel = false;
    this._beforeCacnel = [];
    const cacnelJudge = (rs) => {
      if (this._cancel) {
        return Promise.reject(CancelEerr);
      }
      return Promise.resolve(rs);
    }

    this.prom = this.prom.then(cacnelJudge);

    ['then', 'catch', 'final'].forEach(method => {
      this[method] = fun => {
        if (isDeep) {
          this.prom = this.prom.then(cacnelJudge);
        }
        this.prom = this.prom[method](fun)
        return this;
      }
    });
  }

  cancel() {
    this._beforeCacnel.forEach(item => item());
    this._cancel = true;

    return this;
  }


  // 可能需要在取消前绑定一些事情
  beforeCancel(fun) {
    this._beforeCacnel.push(fun);

    return this;
  }
}

export default CancelPromise

export {
  CancelEerr
}