关于javascript:手写一个promise的过程二

实现promise中then办法的链式调用

const PEDDING = 'PEDDING'const RESOLVE = 'RESOLVE'const REJECT = 'REJECT'// promise 有三种状态const handlePromise = (result,newPromise,resolve, reject)=>{    if(result === newPromise){        throw new Error('不能返回本人')    }    // 返回的是对象或者办法（也能够是promise）    if(typeof result === 'object' && typeof result !== null || typeof result === 'function'){        // 判断result是否有then办法        const then = result.then        if(typeof then === 'function'){            // 如果then办法是一个function 默认是promise            // 调用call办法            then.call(result,r=>{                // 持续调用本人 ，r就是then外面的res                handlePromise(r,newPromise,resolve, reject)            },e=>{                reject(e)            })        }else{            resolve(result)        }    }else{        // 返回一般值        resolve(result)    }}class NewPromise {  // 初始状态为 PEDDING  status = PEDDING  result = undefined  reason = undefined  // 公布订阅者模式  // 目标是为了实现异步  onResolveArr = []  onRejectArr = []  constructor(exc) {    const resolve = (result) => {      if (this.status === PEDDING) {        this.result = result        this.status = RESOLVE        // 执行发布者        this.onResolveArr.map((fn) => fn())      }    }    const reject = (reason) => {      if (this.status === PEDDING) {        this.reason = reason        this.status = REJECT        // 执行发布者        this.onRejectArr.map((fn) => fn())      }    }    exc(resolve, reject)  }  then(onResolve, onReject) {    const newPromise = new NewPromise((resolve, reject) => {      if (this.status === RESOLVE) {        setTimeout(() => {            const result =  onResolve(this.result)            handlePromise(result,newPromise,resolve, reject)                 }, 0)      }      if (this.status === REJECT) {        setTimeout(() => {            const result = onReject(this.reason)            handlePromise(result,newPromise,resolve, reject)        }, 0)      }      // 公布订阅者模式      if (this.status === PEDDING) {        // 将订阅者增加到数组外面        this.onResolveArr.push(() => {            const result = onResolve(this.result)            handlePromise(result,newPromise,resolve, reject)        })        this.onRejectArr.push(() => {            const result = this.onReject(this.reason)            handlePromise(result,newPromise,resolve, reject)        })      }    })    return newPromise  }}// let yan = new Promise((resole, reject) => {//     resole('闫大爷真帅')// })// yan.then(res => {//     console.log(res)// })let newYan = new NewPromise((resole, reject) => {  setTimeout(() => {    resole('new闫大爷真帅')    return '1111'  }, 3000)})newYan  .then((res) => {    console.log(res)    return {name:'yan'}  })  .then((res) => {    console.log(res)  })console.log(11111111)