每日一題之手寫Promise.all和Promise.race

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手寫源碼題是近兩年面試常見的題目，比如對于Promise來說，可能面試官就會讓你手寫Promise.all或者Promise.race, 你能寫出來嗎？

題目一

請手動實(shí)現(xiàn)一個Promise.all，使得下面的測試代碼運(yùn)行正常

Promise.myAll = function(promises) {
  // 請?jiān)诖颂幫晟拼a
}
// 測試代碼
const promise1 = new Promise((_, reject) => {
  setTimeout(() => {
    reject(new Error('報(bào)錯了'))
  },2000)
})
const promise2 = new Promise(resolve => {
  setTimeout(() => {
    resolve('1')
  }, 1000)
})

const promise3 = new Promise(resolve => {
  setTimeout(() => {
    resolve('2')
  }, 999)
})

// 這個應(yīng)該輸出 ['1','2','3'] 順序是固定的
Promise.myAll([promise2,promise3,'3']).then(res => {
  console.log(res)
})

// 這個會進(jìn)入到 catch
Promise.myAll([promise1, promise2,promise3,'3']).then(res => {
  console.log(res)
}).catch(error => {
  console.log('報(bào)錯了')
})

題目二

請手動實(shí)現(xiàn)一個Promise.race，使得下面的測試代碼運(yùn)行正常

Promise.myRace = function(promises) {
  // 請?jiān)诖颂幫晟拼a
}
// 測試代碼
const promise1 = new Promise((_, reject) => {
  setTimeout(() => {
    reject(new Error('報(bào)錯了'))
  },2000)
})
const promise2 = new Promise(resolve => {
  setTimeout(() => {
    resolve('1')
  }, 1000)
})

const promise3 = new Promise(resolve => {
  setTimeout(() => {
    resolve('2')
  }, 999)
})

Promise.myRace([promise1, promise2, promise3]).then(res => {
  // 輸出2
  console.log(res)
})

Promise.myRace([promise1,'3', promise2, promise3]).then(res => {
  // 輸出3
  console.log(res)
})