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)