简化版Promise

class Promise2 {
  #status = 'pending'
  constructor(fn){
    this.q = []
    const resolve = (data) => {
    this.#statys = 'fulfilled'
    const f1f2 = this.q.shift()
    if(!f1f2 || !f1f2[0])return
    const x =f1f2[0].call(undefined,data)
    if(x instanceof Promise2) {
      x.then((data)=>{
        resolve(data)
      }, (reason)=>{
        reject(reason)
      })
    }else{
      resolve(x)
    }
    }
    const reject = (reason)=>{
    this.#status = 'rejected'
    const f1f2 = this.q.shift()
    if(!f1f2 || f1f2[1])return
    const x = f1f2[1].call(undefined, reason)
    if(x instanceof Promise2){
      x.then((data)=>{
       resolve(data)
      },(reason)=>{
       reject(reason)
      })
    }else{
      resolve(x)
    }
    }fn.call(undefined, resolve, reject)
  }
  then(f1, f2){
    this.q.push([f1, f2])
  }
}
const p = new Promise2(function(resolve, reject){
  setTimeout(function(){
  rehect('出错')
  },300)
}) 

p.then((data)=>{console.log(data)},(r)=>{console,eror(r)})