JS Execute functions in order, while passing the next function as an argument

Question

I am trying to eliminate the "callback pyramid of DOOM" by doing this:

$$( //my function
  function(next) { // <- next is the next function
    setTimeout(next,1000); // simple async function
  },

  function(next){ // this function is the previous's function "next" argument
    waitForSomethingAndReturnAValue(next, "I am a parameter!");
  },

  function(aValue){
    console.log("My value is:" + aValue);
  }
);

BUT I have been fiddling for about an hour, and my code doesn't work, any help? this is what I got so far:

function $$(){
  for (a in arguments){
    arguments[a] = function(){
      arguments[a](arguments[Math.max(-1, Math.min(a+1, arguments.length-1))]);
    };
  }
  arguments[0]();
}

you just want to execute several functions in order? You can do an array with the functions you want and make a function executes first function in array and then deleted it — juvian, Mar 29 '14 at 15:30
Yes but I want it so the function itself executes the next function. see code block #1 — Wazzaps, Mar 29 '14 at 15:49
possible duplicate of [Semaphore-like queue in javascript?](http://stackoverflow.com/questions/17528749/semaphore-like-queue-in-javascript) — Benjamin Gruenbaum, Mar 29 '14 at 16:20
Also, consider learning about promises instead of rolling your own asynchronousity abstractions :) — Benjamin Gruenbaum, Mar 29 '14 at 16:20

score 1 · Accepted Answer · answered Mar 29 '14 at 16:15

Something like this works:

function $$() {
    if (arguments.length <= 0) return;
    var args = Array.prototype.slice.call(arguments); // convert to array

    arguments[0](function () { $$.apply(null, args.slice(1)); });
}

$$(function(next) { alert("one"); next() }, function (next) { alert("two"); next() });

http://jsfiddle.net/Cz92w/

score 0 · Answer 2 · answered Mar 29 '14 at 16:13

You can try this:

function $$(){
    var i=0, ret, args = [].slice.call(arguments);
    var obj = {
        next: function() {
            ret = args[i++].call(obj, ret);
        }
    };
    obj.next();
}

and use it like this:

$$(
    function() {
        console.log(Date() + ' - Function 1');
        setTimeout(this.next, 1e3); // simple async function
    },
    function(){
        console.log(Date() + ' - Function 2');
        return waitForSomethingAndReturnAValue(this.next, "I am a parameter!");
    },
    function(aValue){
        console.log(Date() + ' - Function 3');
        console.log("My value is:" + aValue);
    }
);
function waitForSomethingAndReturnAValue(callback, param) {
    setTimeout(callback, 2e3);
    return param + param;
}

Basically, the returned value in each function is passed as the argument to the next one. And the reference to the next function is this.next.

JS Execute functions in order, while passing the next function as an argument

2 Answers2