Question

In some places we have to have only one instance of function running.

This code works for me:

function example() { 
    var that = this; 
    if(that.running) { 
       return false; 
    }
    that.running = true; 
    $.get(url, {}, function (data) {
         that.running = false; 
    }); 
}

How we can improve it, and make it more reusable?

UPD Here is solution, based on Frits van Campen answer:

function make_run_once(callback) {
    callback.running = false;
    return function () {
        if(callback.running) {
            return false;
        }
        callback.running = true;
        deferred = $.Deferred();
        deferred.done(function () {
            callback.running = false;
        });
        callback(deferred);  // pass deferred to callback so it can resolve at it's own leisure
    };
}

Answer 1

You might want to use jQuery’s `Deferred’ functionality for that:

function decorate(fn) {
    var deferred;
    return function(){
        if (!deferred) {
            deferred = new jQuery.Deferred;
            fn(deferred.resolve); // pass in the callback
        }
        return deferred;
    };
}

A decorated function will always return the same Deferred object, which will be resolved with the callback from the original function – started on the first invocation.