手写Promise最终版

const PROMISE_STATUS_PENDING = 'pending'
const PROMISE_STATUS_FULFILLED = 'fulfilled'
const PROMISE_STATUS_REJECTED = 'rejected'

function execFunctionWithCatchError(exec, value, resolve, reject) {
  try {
    const result = exec(value)
    resolve(result)
  } catch (err) {
    reject(err)
  }
}

class MyPromise {
  constructor(executor) {
    this.status = PROMISE_STATUS_PENDING
    this.value = undefined
    this.reason = undefined
    this.onFulfilledFns = []
    this.onRejectedFns = []

    const resolve = (value) => {
      if (this.status === PROMISE_STATUS_PENDING) {
        queueMicrotask(() => {
          if (this.status !== PROMISE_STATUS_PENDING) return
          this.value = value
          this.status = PROMISE_STATUS_FULFILLED
          this.onFulfilledFns.forEach(fn => {
            fn(this.value)
          })
        })
      }
    }

    const reject = (reason) => {
      if (this.status === PROMISE_STATUS_PENDING) {
        queueMicrotask(() => {
          if (this.status !== PROMISE_STATUS_PENDING) return
          this.reason = reason
          this.status = PROMISE_STATUS_REJECTED
          this.onRejectedFns.forEach(fn => {
            fn(this.reason)
          })
        })
      }
    }

    try {
      executor(resolve, reject)
    } catch (err) {
      reject(err)
    }
  }

  then(onFulfilled, onRejected) {
    const defaultOnRejected = err => { throw err }
    onRejected = onRejected ?? defaultOnRejected

    const defaultOnFulfilled = value => { return value }
    onFulfilled = onFulfilled ?? defaultOnFulfilled

    return new MyPromise((resolve, reject) => {
      if (this.status === PROMISE_STATUS_PENDING) {
        this.onFulfilledFns.push(() => {
          execFunctionWithCatchError(onFulfilled, this.value, resolve, reject)
        })
          this.onRejectedFns.push(() => {
            execFunctionWithCatchError(onRejected, this.reason, resolve, reject)
          })
      }
      if (this.status === PROMISE_STATUS_FULFILLED) {
        execFunctionWithCatchError(onFulfilled, this.value, resolve, reject)
      }
      if (this.status === PROMISE_STATUS_REJECTED) {
        execFunctionWithCatchError(onRejected, this.reason, resolve, reject)
      }
    })
  }

  catch(onRejected) {
    return this.then(undefined, onRejected)
  }

  finally(onFinally) {
    this.then(() => {
      onFinally()
    }, () => {
      onFinally()
    })
  }

  static resolve(value) {
    return new MyPromise((resolve) => resolve(value))
  }

  static reject(reason) {
    return new MyPromise((resolve, reject) => reject(reason))
  }

  static all(promises) {
    // 问题关键: 什么时候执行resolve 什么时候执行reject
    return new MyPromise((resolve, reject) => {
      const values = []
      promises.forEach((promise) => {
        promise.then(res => {
          values.push(res)
          if (values.length === promises.length) {
            resolve(values)
          }
        }, err => {
          reject(err)
        })
      })
    })
  }

  static allSettled(promises) {
    return new MyPromise((resolve, reject) => {
      const values = []
      promises.forEach(promise => {
        promise.then(res => {
          values.push({ status: PROMISE_STATUS_FULFILLED, value: res })
          if (values.length === promises.length) {
            resolve(values)
          }
        }, err => {
          values.push({ status: PROMISE_STATUS_REJECTED, value: err })
          if (values.length === promises.length) {
            resolve(values)
          }
        })
      })
    })
  }

  static race(promises) {
    return new MyPromise((resolve, reject) => {
      promises.forEach(promise => {
        promise.then(resolve, reject)
      })
    })
  }

  static any(promises) {
    return new MyPromise((resolve, reject) => {
      const reasons = []
      promises.forEach(promise => {
        promise.then(resolve, err => {
          reasons.push(err)
          if (reasons.length === promises.length) {
            reject(new AggregateError(reasons))
          }
        })
      })
    })
  }
}

const promise1 = new MyPromise((resolve, reject) => {
  setTimeout(() => { reject(111) }, 1000)
})

const promise2 = new MyPromise((resolve, reject) => {
  setTimeout(() => { reject(222) }, 2000)
})

const promise3 = new MyPromise((resolve, reject) => {
  setTimeout(() => { reject(333) }, 3000)
})

MyPromise.any([promise1, promise2, promise3]).then(res => {
  console.log("res: ", res)
}).catch(err => {
  console.log("err: ", err)
})