问题描述

您好，这是一个帮助我了解 Promises .then 如何返回工作的问题.问题是:如何将变量范围限定为第二个 .then 链式函数?

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?

这是一个 jsbin http://jsbin.com/xacuna/edit?js,output

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

我可以访问全局变量，然后将作用域变量传递给第一个，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}`)
})

推荐答案

当你使用 ES2015 - 简单的解决方案使用 对象速记属性名称 和 对象解构

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}`)
})

这篇关于承诺，如何将变量传递给 .then 函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！