Question

I’m looking for a Thread.Join() type thing. Lets say I trigger 4 events in javascript. I want to execute code but only after all 4 callbacks have been completed. How do I do that? The only way I can think of is checking if any the 4 callbacks are in process via global var in which case i ignore or throw exception. But otherwise do something like globalVar++ in each callback and call IsItDone() at the end of each callback which checks if the globalVar is == 4.

But.. I kind of dont like it especially since I need to use a global var.

Answer 1

If you don’t mind adding jQuery to your site you can use its “deferred object” capability.

Each async function (include jQuery’s built-in AJAX functions) can return a “promise” to return something later.

To achieve what you’re asking for you can then call:

$.when(p1, p2, p3, p4).done(function() {
    // this will be called only when
    // all of p1 - p4 have been "resolved"
});

If you prefer to have an array p containing those promises instead, call $.when like this instead:

$.when.apply($, p).done(function() {
    ...
});