jQuery callback for multiple ajax calls

Question

I want to make three ajax calls in a click event. Each ajax call does a distinct operation and returns back data that is needed for a final callback. The calls themselves ar

Answer 1

It's not jquery (and it appears jquery has a workable solution) but just as another option....

I've had similar problems working heavily with SharePoint web services - you often need to pull data from multiple sources to generate input for a single process.

To solve it I embedded this kind of functionality into my AJAX abstraction library. You can easily define a request which will trigger a set of handlers when complete. However each request can be defined with multiple http calls. Here's the component (and detailed documentation):

DPAJAX at DepressedPress.com

This simple example creates one request with three calls and then passes that information, in the call order, to a single handler:

    // The handler function 
function AddUp(Nums) { alert(Nums[1] + Nums[2] + Nums[3]) }; 

    // Create the pool 
myPool = DP_AJAX.createPool(); 

    // Create the request 
myRequest = DP_AJAX.createRequest(AddUp); 

    // Add the calls to the request 
myRequest.addCall("GET", "http://www.mysite.com/Add.htm", [5,10]); 
myRequest.addCall("GET", "http://www.mysite.com/Add.htm", [4,6]); 
myRequest.addCall("GET", "http://www.mysite.com/Add.htm", [7,13]); 

    // Add the request to the pool 
myPool.addRequest(myRequest); 

Note that unlike many of the other solutions (including, I believe the "when" solution in jquery) provided this method does not force single threading of the calls being made - each will still run as quickly (or as slowly) as the environment allows but the single handler will only be called when all are complete. It also supports the setting of timeout values and retry attempts if your service is a little flakey.

I've found it insanely useful (and incredibly simple to understand from a code perspective). No more chaining, no more counting calls and saving output. Just "set it and forget it".