async与await

朴灿烈づ我的快乐病毒、 2021-10-01 06:02 296阅读 0赞

function test () {
      return new Promise(resolve => {
        setTimeout(() => {
          console.log('test')
          resolve()
        }, 1000)
      })
    }
    function test1 () {
      return new Promise(resolve => {
        setTimeout(() => {
          console.log('test1')
          resolve()
        }, 1000)
      })
    }
    function test2 () {
      return new Promise(resolve => {
        setTimeout(() => {
          console.log('test2')
          resolve()
        }, 1000)
      })
    }
    async function call () {
      await test()
      await test1()
      await test2()
    }
    call ()

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继发执行

function call () {
      Promise.all([test(), test1(), test2()])
    }
    call()

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function getUserInfo (id) {
      return new Promise(resolve => {
        setTimeout(() => {
          resolve({
            id: id,
            name: 'xxx',
            age: 'xxx'
          })
        }, 200)
      })
    }
    const users = [{id: 1}, {id: 2}, {id: 3}]
    let userInfos = []
    users.forEach(async user => {
      let info = await getUserInfo(user.id)
      userInfos.push(info)
    })
    console.log(userInfos) // []

function getUserInfo (id) {
      return new Promise(resolve => {
        setTimeout(() => {
          resolve({
            id: id,
            name: 'xxx',
            age: 'xxx'
          })
        }, 200)
      })
    }
    const users = [{id: 1}, {id: 2}, {id: 3}]
    let userInfos = []
    async function call() {
      for (user of users) {
        let info = await getUserInfo(user.id)
        userInfos.push(info)
      }
      console.log(userInfos)
    }
    call()

继发式的

function getUserInfo (id) {
      return new Promise(resolve => {
        setTimeout(() => {
          resolve({
            id: id,
            name: 'xxx',
            age: 'xxx'
          })
        }, 200)
      })
    }
    const users = [{id: 1}, {id: 2}, {id: 3}]
    let userInfos = []
    const promises = users.map(user => getUserInfo(user.id))
    Promise.all(promises).then(res => {
      userInfos = res
      console.log(userInfos)
    })

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