jQuery/Javascript Delay Execution of a Function Until Several Functions Have Completed

Question

I have a tricky situation. I need to delay execution of a function until several functions have completed. While the following would work in a normal situation:

    $.when(foo1(), foo2(), foo3()).then(function(){
        //foo4();
    });

My situation is a little different. I don't want the functions passed to $.when() to execute immediately. foo1-3 will be executed at some point in the near future, by other methods. In other words, I want to execute foo1-3 manually, at a time of my choosing. Only after foo1-3 have executed (in no specific order) will foo4 run.

My intuition told me to dig into $.Deferred(), but I haven't quite found what I need. Any ideas?

You meant .then(foo4), right? Otherwise you're passing the value returned by foo4() to .then()... — Matt Ball
– Matt Ball, Commented Aug 7, 2012 at 18:44

Matt Ball · Accepted Answer · 2012-08-07 18:40:27Z

3

Have the fooX functions resolve deferreds which are passed to $.when.

var d1 = $.Deferred();
var d2 = $.Deferred();
var d3 = $.Deferred();

function foo1() {
    // do normal work, then
    d1.resolve();
}

// same for other 2 functions

$.when(d1, d2, d3).then(foo4);

http://jsfiddle.net/mattball/nVFnv/

answered Aug 7, 2012 at 18:40

Matt Ball

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Diodeus - James MacFarlane · Accepted Answer · 2012-08-07 18:38:45Z

2

Make a scoreboard variable that counts up as each function completes, then call foo4 after each function. foo4 should exit if the score has not counted up to the correct value.

answered Aug 7, 2012 at 18:38

Diodeus - James MacFarlane

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2 Comments

Pop-A-Stash Over a year ago

Ok. Not bad. I had that idea myself. Was looking for something more elegant. But, "by hook or crook" is certainly an option.

Pop-A-Stash Over a year ago

The answer by Matt Ball is essentially your idea, just using deferred objects instead of a scoreboard variable. Thanks!

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