What is the most efficient way to create map of functions to arguments?

Question

I want to create a map of functions to its argument. This map will be updated dynamically. Finally all the functions will be called with their corresponding arguments.

Answer 1

Credits to Dagg Nabbit for suggesting this in the comments under my question.

"Don't forget functions can have properties. You could always store the functions in an array, and attach their index in the array to the function as a propery, and look them up that way." - Dagg Nabbit

Consider the following map of args-to-callback arguments :

map :

1 -> foo1
2 -> foo1,foo2
3 -> foo2

The objective is to construct a callback-to-args map (reverse map) like this :

callbackMap:

foo1 -> [1,2]
foo2 -> [2,3]

Approach :

var allArgsPossible = [1,2,3]

// contains the list of callbacks to be called
var callbackArray = [];  

//maps the callback index in callbackArray to the callback's arguments
//callbackMap[index] = args means callbackArray[index] will be called with parameter "args" 
var callbackMap = {};

for( i in allArgsPossible)
{
    var item = allArgsPossible[i];
    var callbacks =  map[ item  ];
    for(j in callbacks)
    {
        var callback = callbacks[j];

        if(callback.index == undefined)
        {
            var index = callbackArray.length;
            // adding a new property "index" to the callback
            callback.index = index;
            callbackMap[index] = [item];
            //create a new entry in callbackArray
            callbackArray.push(callback);
        }
        else
        {
            callbackMap[callback.index].push(item);
        }
    }
}

console.log(JSON.stringify(callbackMap));

for( i in callbackArray)
{
    var callback = callbackArray[i];
    //get arguments from our reverse map
    var args = callbackMap[callback.index];
    // Bingo ! 
    callback(args);
}

You can get the whole picture here : http://jsfiddle.net/kyvUA/2/

One point to note here is that the callback function may already have an "index" property for some other purpose. If that is a concern, you can generate a random string and store this property on the callback with the index as the value. ( as suggested by @plalx )

Cheers !