How to return value from an asynchronous callback function? [duplicate]

by

This is impossible as you cannot return from an asynchronous call inside a synchronous method.

In this case you need to pass a callback to foo that will receive the return value

function foo(address, fn){
  geocoder.geocode( { 'address': address}, function(results, status) {
     fn(results[0].geometry.location); 
  });
}

foo("address", function(location){
  alert(location); // this is where you get the return value
});

The thing is, if an inner function call is asynchronous, then all the functions ‘wrapping’ this call must also be asynchronous in order to ‘return’ a response.

If you have a lot of callbacks you might consider taking the plunge and use a promise library like Q.

More Related Contents:

  1. Callback after all asynchronous forEach callbacks are completed
  2. I know that callback function runs asynchronously, but why?
  3. How should I call 3 functions in order to execute them one after the other?
  4. How to “await” for a callback to return?
  5. nodeJs callbacks simple example
  6. How can I take advantage of callback functions for asynchronous XMLHttpRequest?
  7. Waiting on multiple asynchronous calls to complete before continuing
  8. Converting a recursive function into an asynchronous CPS implementation (javascript)
  9. Asynchronous Script Loading Callback
  10. How to make non-blocking javascript code?
  11. Does an async function always need to be called with await?
  12. javascript: execute a bunch of asynchronous method with one callback
  13. Load javascript async, then check DOM loaded before executing callback
  14. How can I upload files asynchronously with jQuery?
  15. console.log() async or sync?
  16. How to iterate over a JavaScript object?
  17. JavaScript: Passing parameters to a callback function
  18. How can I wait for set of asynchronous callback functions?
  19. How to transpose a javascript object into a key/value array
  20. $.Deferred: How to detect when every promise has been executed
  21. How to return an Ajax result using async/await? [duplicate]
  22. newbie approach: what is a javascript callback function?
  23. How do image preloaders work?
  24. What’s the difference between “{}” and “[]” while declaring a JavaScript array?
  25. Elegant way to copy only a part of an object [duplicate]
  26. Using JavaScript what’s the quickest way to recursively remove properties and values from an object?
  27. How does javascript async/await actually work?
  28. jQuery ajax async: false causes a strange warning?
  29. Await an iterative function without delimiter in JS
  30. JavaScript Callback after calling function

Leave a Comment