Javascript, value types as reference

Question

I've some scenarios where i need to pass value type as reference without changed the processing function.

1. Example Numeric Types (var limit)

   var limit = 0; // Need to be the reference type
   var multiCallback = new MultiCallback(limit, function(){});
   for (element in myObject)
   {
    limit++;
    element.DoSomething(multiCallback.callback);
   }
   function MultiCallback(limit, func)
   {
    var calls = 0;
    function callback()
    {
    if (++calls == limit)
    {
    func();
    }
    }
    return {
    callback : callback
    }
   }
   

2. Examble Function Types

   var resizeCallback = function(){};
   $(window).resize(resizeCallback);
   function showPage()
   {
    resizeCallback = resizePage();
   }
   function showLoader()
   {
    resizeCallback = resizeLoader();
   }
   

is there a solution

• Matt: You can't (without changed the processing function...). Numbers and strings in JavaScript are immutable.
• Felix Kling: possible duplicate of Pass Variables by Reference in Javascript

Answer 1

Changing the value of a variable will never update the previous value of the variable.

For functions, you can do something like this:

var current = function() { ... };
function resizeCallback() {
 return current.apply(this, arguments);
}
// Updating current will work:
current = function() { ... something ... };

For other values (primitives and objects), the closest thing is to pass an object:

var limit = {value: 0};
function MultiCallback(limit, func) {
 ....
 if (limit.value == ++calls) ...
}
// Changing limit:
limit.value = 1;

Answer 2

There is no pass by reference in javascript (assigning arguments is not visible to the caller). What you are doing in your function example is modifying a global variable.

You can wrap it with an object and mutations of that object are visible to the caller:

var limit = {
 value: 0 
};