I am having a really peculiar case. I want to return some data - data that is downloaded via ajax. So far async & sync modes don't get the data in time to the return. Is it possible I could either call return from a child function for the parent function or could a timeOut solve the issue? I can't think of another way of doing this, but the data must be returned.

I am having a really peculiar case. I want to return some data - data that is downloaded via ajax. So far async & sync modes don't get the data in time to the return. Is it possible I could either call return from a child function for the parent function or could a timeOut solve the issue? I can't think of another way of doing this, but the data must be returned.

• javascript
• ajax
• return

• return is NOT a function! Though perhaps raising an exception could do what you want? – Ponkadoodle Commented Feb 26, 2010 at 0:33
• Is there a certain way that an exception could return an array just like return? – Kyle Hotchkiss Commented Feb 26, 2010 at 0:56
• Perhaps it would have been appropriate to tell in your function that you are using jQuery? – zneak Commented Feb 26, 2010 at 0:57
• 1 possible duplicate of how to return value to parent function from nested anonymous function – Patsy Issa Commented Aug 18, 2015 at 10:54

3 Answers 3

You could provide a callback function:

function parentfunction(callback) {
    callback(getAjax());
}

function childfunction() {
    parentfunction(function(ajaxData) {
        //Do stuff with data
    });
}

The answer to your question is no.

In asynchronous requests, the function has to return before the result is available. To work around this, a callback pattern is used - when calling such a function, you don't expect a return, but rather provide it with a callback - a function to be called once the result is available.

Here's a simple example:

var someValue;
fetchValueFrom('http://example./some/url/with/value', function(val) { 
  someValue = val; 
  doSomethingElseWith(someValue);
});

Here we create a function and pass it in as a second param to the fetchValueFrom call. Once the value is available this function will be called, and will set the variable and call another function to continue execution.

Just pass false as a third parameter to to XMLHttpRequest.open. It means "run this query synchronously".

See the reference for yourself.