封装Promise

class myPromise {
    constructor(callback) {
      this.callback = callback;
      this.status = 'pendding';
      this.result = null;
      this.err = null;
      this.resolveR = null;
      this.rejectR = null;
      this.resolve = val => {
          this.status = 'resolve';
          this.result = val;
          this.resolveR && this.resolveR(val);
      }
      this.reject = err => {
        this.status = 'reject';
        this.err = err;
        this.rejectR && this.rejectR(err);
      }
      this.callback(this.resolve, this.reject);
    }
    then(callback) {
      this.status === 'resolve' ? callback(this.result) : this.resolveR = callback;
      return new myPromise(this.callback);
    }
    catch(callback) {
      this.status === 'reject' ? callback(this.err) : this.rejectR = callback;
      return new myPromise(this.callback);
    }
  }
  new myPromise((resolve, reject) => {
    setTimeout(() => {
      resolve(1);
    }, 1000);
  }).then(res => {
    console.log(res)
  }).catch(err => {
    console.log(err)
  })

简单的总结，希望对大家有所帮助，如有不对的地方也烦请指出，谢谢！