概况

在node中经常在循环中用到promise, 分串行和并行,那怎么样去写呢

实施

串行

const arr = [1, 2, 3, 4]
const promise1 = async (value) => {
return new Promise(resolve => {
  setTimeout(() => {
    resolve(value)
  }, 1000)
}
cx()

并行

const bx = async () => {
const promiseArr = []
for(let value of arr){
  promiseArr.push(promise1(value))
}
const data = await Promise.all(promiseArr)
console.log('data', data)
}
bx()

同时执行

const arr = [1, 2, 3, 4]
const promise1 = async (value) => {
  return new Promise(resolve => {
    setTimeout(() => {
      resolve(value)
    }, 1000)
  })
}
const cx = async () => {
  for(let value of arr){
    const data = await promise1(value)
    console.log('data', data)
  }
}

const bx = async () => {
  const promiseArr = []
  for(let value of arr){
    promiseArr.push(promise1(value))
  }
  const data = await Promise.all(promiseArr)
  console.log('data', data)
}
cx()
bx()
/*
data 1
data [ 1, 2, 3, 4 ] 并行比串行快
data 2
data 3
data 4
*/