Question

196

Promise inside promise: what's the correct way to return a variable from the child promise? (JS)

rated 0 times [ 197] [ 1] / answers: 1 / hits: 92390 / 7 Years ago, wed, may 10, 2017, 12:00:00

I've a function like this:

function top() {



  //promise1

  ParentPromise({

    ...some code here...

  }).then(function() {





    //promise2

        ChildPromise({

          ..some code here...

        }).then(function(response) {

         var result = response.result.items;



        });



});



};

and i need to return result value in this way:

var myresult = start();

How i can do that? THX

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everardo

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4 Years ago

answered 7 Years ago jadyngraysons · Accepted Answer

The definition of promises is that you cannot literally assign result to myresult. However, you can make myresult a promise that resolves directly to result for the caller, however many promises were used to get that. The basic idea is that inside of each function in your above block, you should be returning the next Promise in the chain. eg:

function top() {



  //promise1

  return ParentPromise({

    ...some code here...

  }).then(function() {





    //promise2

        return ChildPromise({

          ..some code here...

        }).then(function(response) {

         var result = response.result.items;

         return result;



        });



});



};

In the end, the code calling top() won't know or care that 1, 2, or 12 chained promises were used to get result. It will also be able to register an error callback in case any of those promises failed.