JavaScript Function Queue

Question

I have a ton of functions that need to run in succession, but not before the other has completed. What I need is a way to queue these functions to run only after the previous function was successfully completed. Any Ideas?

Function1();
Function2();
Function3();
Function4();
Function5();

Answer 1

You could use something like this:

var FunctionQueue = (function(){
    var queue = [];
    var add = function(fnc){
        queue.push(fnc);
    };
    var goNext = function(){
        var fnc = queue.shift();
        fnc();
    };
    return {
        add:add,
        goNext:goNext
    };
}());

and use it like this:

var fnc1 = function(){
    window.setTimeout(function(){
        alert("1 done");
        FunctionQueue.goNext();
    }, 1000);
};

var fnc2 = function(){
    window.setTimeout(function(){
        alert("2 done");
        FunctionQueue.goNext();
    }, 5000);
};

var fnc3 = function(){
    window.setTimeout(function(){
        alert("3 done");
        FunctionQueue.goNext();
    }, 2000);
};

FunctionQueue.add(fnc1);
FunctionQueue.add(fnc2);
FunctionQueue.add(fnc3);
FunctionQueue.goNext();

Edit after a few years: Another way people are approaching this is to pass in a next function that you can call to continue the chain. Like so:

var Queue = function(arr){
    var index = 0;
    var next = function(){
        if (index >= arr.length) {return;}
        arr[index++](next);
    };
    return next;
};

var fn1 = function(next){
    console.log("I am FN1");
    next();
};

var fn2 = function(next){
    console.log("I am FN2");
    setTimeout(next,1000);
};

var fn3 = function(next){
    console.log("I am FN3");
    setTimeout(next,3000);
};

var fn4 = function(next){
    console.log("I am FN4");
    setTimeout(next,1000);
};

Queue([fn1, fn2, fn3, fn4])();