Question

Can we pass a reference of a variable that is immutable as argument in a function?

Example:

var x = 0;
function a(x)
{
    x++;
}
a(x);
alert(x); //Here I want to have 1 instead of 0

Answer 1

Since JavaScript does not support passing parameters by reference, you’ll need to make the variable an object instead:

var x = {Value: 0};

function a(obj)
{
    obj.Value++;
}

a(x);
document.write(x.Value); //Here i want to have 1 instead of 0

In this case, x is a reference to an object. When x is passed to the function a, that reference is copied over to obj. Thus, obj and x refer to the same thing in memory. Changing the Value property of obj affects the Value property of x.

Javascript will always pass function parameters by value. That’s simply a specification of the language. You could create x in a scope local to both functions, and not pass the variable at all.