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Promise的多种写法

英乐 2022-03-18 阅读 60

一般写法:

  new Promise((resolve,reject) => {
    setTimeout(() => {
      resolve()
      reject()
    }, 1000)
  }).then(
    console.log("Hello Promise")
  ).catch(() =>{
    console.log('error')
  })

简易的then写法:

传输数据时的原始写法:

  new Promise((resolve, reject) =>{
    setTimeout(() => {
      console.log('1')
      resolve('1')
    }, 1000)
  }).then((data) =>{
    console.log(data + '1')

    return new Promise((resolve,reject) => {
      setTimeout(() => {
        resolve(data + '1')
      },1000)
    })
  }).then((data) =>{
    console.log(data + '1')

    return new Promise((resolve,reject) => {
      setTimeout(() => {
        resolve(data + '1')
      },1000)
    })
  })

 

 

 

传输数据时的简易写法:

 

 Promise.all的写法;(应用场景在于需求建立在多次请求后)

  Promise.all([ 
    new Promise((resolve,reject) => {
      setTimeout(() =>{
        resolve('demo1')
      },1000)
    }),
    new Promise((resolve,reject) => {
      setTimeout(() =>{
        resolve('demo2')
      },1000)
    })
  ]).then(results => {
    console.log(results)
  })

(请求了demo1和demo2数据后一起进行打印) 

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