Promises, how to pass variable into .then function

Question

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?

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

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}`)
})

Solution

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}`)
})

Comments

[Jaromanda X]

the callback in then only accepts a single argument - an object would be useful

[jfriend00]

See How to share prior results when chaining promises.