简单模拟实现Promise部分功能

只是简单的实现Promise部分功能，.catch和.finally以及类方法都没有实现，感兴趣的可以再继续深入研究

      // 简单手写部分Promise
      const PROMISE_STATUS_PENGING = "pending"
      const PROMISE_STATUS_FULFILLED = "fulfilled"
      const PROMISE_STATUS_REJECTED = "rejected"
      class myPromise{
        // 构造函数接收Promise回调，回调接收两个参数在构造函数里定义
        constructor(executor){
          //状态管理，执行了resolve就不执行reject
          this.status = PROMISE_STATUS_PENGING 
          // 存放resolve和reject传的参数 
          this.value = undefined
          this.reason = undefined
          const resolve = (value)=>{
            // 状态判断
            if(this.status === PROMISE_STATUS_PENGING){
              this.status = PROMISE_STATUS_FULFILLED
              console.log("执行");
              queueMicrotask(()=>{    //微任务延迟执行  setTimeout为宏任务
                this.value = value
                console.log("resolve被执行");
                if(this.onFulfilled){
                  this.onFulfilled(this.value)
                }
              })
            }
          }
          const reject = (reason)=>{
            if(this.status === PROMISE_STATUS_PENGING){
              this.status = PROMISE_STATUS_REJECTED
              queueMicrotask(()=>{   
                this.reason = reason
                console.log("reject被执行");
                if(this.onRejected){
                  this.onRejected(this.reason)
                }
              })
            }
          }
          // 执行Promise
          executor(resolve,reject)
        }
        // 绑定resolve和reject后要执行的函数，在上述微任务执行之前已绑定
        then(onFulfilled,onRejected){
          this.onFulfilled = onFulfilled
          this.onRejected = onRejected
        }
      }
      const p = new myPromise((resolve,reject)=>{
        // 执行了resolve就不执行reject验证
        resolve("成功")
        reject("失败")
      })
      console.log(1111);
      // .then属于主线程任务，执行then后才开始执行上行resolve内的微任务
      p.then(res=>{
        console.log('res: ', res);
      },err=>{
        console.log('err: ', err);
      })

打印结果