問題描述

您好，這是一個幫助我了解 Promises .then 如何返回工作的問題.問題是:如何將變量范圍限定為第二個 .then 鏈式函數?

Hello this is a question to help me understand how Promises .then returns work. The question is: how can I scoped variables to the second .then chained function?

這是一個 jsbin http://jsbin.com/xacuna/edit?js,output

Here is a jsbin http://jsbin.com/xacuna/edit?js,output

我可以訪問全局變量，然后將作用域變量傳遞給第一個，而不是之后.

I can access the global variables, and pass in the scoped variables to the first then, but not after.

  let innerReturnFunction = (res, myName) => {
    /* this works */
    console.log(`hi from inner name: ${myName}`)
    return res
  }

 let getInnerFuncVariable = () => {
   var myName = 'arturo'

   return fetch('https://httpbin.org/get')
    .then(function (res) {
      myName = 'Bob'
      return innerReturnFunction(res, myName);
    })
    .then(function (res, myName) {
      /* doesn't work, how can I access myName */
      console.log(`in first then ${res.url}, ${myName}`)
    });
 }

getInnerFuncVariable().then(function(res, myName) {
  /* how can I access myName */
  console.log(`last called ${myName}`)
})

推薦答案

當你使用 ES2015 - 簡單的解決方案使用 對象速記屬性名稱 和 對象解構

as you are using ES2015 - easy solution uses object Shorthand property names and Object destructuring

let innerReturnFunction = ({res, myName}) => {
    /* this works */
    console.log(`hi from inner name: ${myName}`);
    return {res, myName}; // return an object
}

let getInnerFuncVariable = () => {
    var myName = 'arturo';

    return fetch('https://httpbin.org/get')
        .then(function(res) {
            myName = 'Bob'
            return innerReturnFunction({res, myName});
        })
        .then(function({res, myName}) {
            console.log(`in first then ${res.url}, ${myName}`);
            return {res, myName};// ADD THIS!!
        });
}

getInnerFuncVariable().then(function({res, myName}) {
    console.log(`last called ${myName}`)
})

這篇關于承諾，如何將變量傳遞給 .then 函數的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！