Asynchronous Loop of jQuery Deferreds (promises)

Question

I am trying to create what I think is referred to as a \"Waterfall\". I want to sequentially process an array of async functions (jQuery promises).

Here\'s a contr

Answer 1

Interesting challenge indeed. What I have come up with is a recursive function that accepts a list and an optional start index.

Here is a link to the jsFiddle that I have tested with a few different list lengths and intervals.

I'm assuming you have a list of functions that return promises (not a list of numbers). If you do have a list of numbers you would change this part

$.when(tasks[index]()).then(function(){
    deferredSequentialDo(tasks, index + 1);
});

to this

/* Proxy is a method that accepts the value from the list
   and returns a function that utilizes said value
   and returns a promise  */
var deferredFunction = myFunctionProxy(tasks[index]);

$.when(tasks[index]()).then(function(){
    deferredSequentialDo(tasks, index + 1);
});

I'm not sure how big your list of functions could be but just be aware that the browser will hold on to the resources from the first deferredSequentialDo call until they are all finished.