waiting for async callback, then return

Question

Here is a function that I would like to call for its return value, and in that function I would like to use an async call that would set a flag to work with later on:

function getSomething() {
    var isOk;

    myAsyncFunction(function(data) {
        if (data === 'foo') {
            isOk = true;
        }
    });

    //...

    if (isOk) {
        return true;
    }
}

I would want to use getSomething() like this:

if (getSomething()) {...}

I know that it won't pause the execution of this function to wait for my async call to finish. I also know that the return true statement should not be in the callback of the async function. But how can I wait for the async function's callback? Should I transform my getSomething() call to a promise or is there another way? And how would be the call of getSomething() look like if I'd use promises? Thanks in advance!

`myAsyncFunction` should return a promise, you should return that promise from `getSomething`. — Kevin B, Sep 16 '15 at 18:08
*"But how can I wait for the async function's callback?"* you can't, that isn't possible. The only option is to use callbacks, either directly or on promise objects. — Kevin B, Sep 16 '15 at 18:09

score 0 · Answer 1 · answered Sep 16 '15 at 18:09

0

You can use JavaScriptPromise

var promise = new Promise(function(resolve, reject) {


  if (/* everything turned out fine */) {
    resolve("worked!");
  }
  else {
    reject(Error("broke"));
  }
});

How to use

promise.then(function(result) {
  console.log(result); // "worked!"
}, function(err) {
  console.log(err); // Error: "broke"
});

For more information you can visit this link Promise

answered Sep 16 '15 at 18:09

santosh singh

27,666
26
83
129

2

But you still can't use the return value in an `if`. You can't **wait** for asynchronous actions. – Barmar Sep 16 '15 at 18:23

waiting for async callback, then return

1 Answers1