Queueing a function call request javascript

Question

I have a function like this

function queuingFunction(name){

        var deferred = $q.defer()

        $timeout(function(){
            console.log("my name is ",name);
            deferred.resolve(true);
        },3000)

        return deferred.promise;
    }

i am calling the function like this

communicatorBaseService.queuingFunction("Jack"); communicatorBaseService.queuingFunction("max"); communicatorBaseService.queuingFunction("Ray");

In the console all the 3 results are displayed after 3 second.

What i need is , at the 3rd second Jack shows in console, after again 3 seconds max is shown then again after 3 second Ray is shown.

If i call queuingFunction in between the execution it should get added to a execution queue.

What i was thinking to do was

Receive the request to execute the function
Add the params to a queue
Call the queuingFunction with the queue
Run the queuingFunction with the queue[0]
On complete of queuingFunction delete the queue[0]
Check if anything is left at position queue[0] re-run the function with the current queue.

Pretty sure this is not the best way, what can be a good way to do this. I am using Angular thus $q is there in code. I don't want to use jQuery.

jfriend00 · Accepted Answer · 2015-10-08 08:04:39Z

3

It sounds from your comments like you want to be able to just make some function call and have it's operation automatically sequenced with the ones that came before. If so, you will need some sort of queue object that can accumulate the operations underway and pending.

Promises already are a sort of queue, so if you can start with a promise and just add a new promise onto the end of the prior operation each time you make your function call, it can sequence them. Here's one way to do that:

// initialize queue with a resolved promise
var queue = $q();

function queuingFunction(name){
    // chain this operation onto whatever operation was previously queued
    queue = queue.then(function() {
        var deferred = $q.defer()

        $timeout(function(){
            console.log("my name is ",name);
            deferred.resolve(true);
        },3000)

        return deferred.promise;
    });
}

Then, you can just call:

queuingFunction("Jack"); 
queuingFunction("max"); 
queuingFunction("Ray");

And, the three operations will be sequential.

Here's a working demo using ES6 standard promises: http://jsfiddle.net/jfriend00/adq3L6zt/

edited Oct 8, 2015 at 8:04

answered Oct 8, 2015 at 7:57

jfriend00

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2 Comments

Gaurav_soni Over a year ago

Yes this is exactly what i was looking for as per your fiddle. Im just trying to do it in angular using the $q as i have used this primary in my project.

jfriend00 Over a year ago

@Gaurav_soni - I don't use $q myself (much prefer standard ES6 promises), but I put my guess as the code in my answer. The only thing I'm not sure of is $q() for manufacturing a resolved promise to initialize the queue. If that doesn't work, then you can do it a longer way by creating a deferred and then resolving it and assign to queue.

Gaurav_soni · Accepted Answer · 2015-10-08 11:34:06Z

0

Using @jfriend00 approach I did the following using angular $q if anyone interested

var queue = $q(function(resolve,reject){resolve()});

        service.queuingFunction = function(name){
          // perform some asynchronous operation, resolve or reject the promise when appropriate.
          queue = queue.then(function() {
                var deferred = $q.defer()

                $timeout(function(){
                    console.log("my name is ",name);
                    deferred.resolve(true);
                },3000)

                return deferred.promise;
            });
        }

answered Oct 8, 2015 at 11:34

Gaurav_soni

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