How can I attach a change event handler to a variable? [duplicate]

Question

Possible Duplicate:
Listening for variable changes in JavaScript or jQuery

How can I track if this variable has changed?

var ConditionalFlag = 0;

I tried this:

var ConditionalFlag = 0;
$(ConditionalFlag).change(function () {
    alert("Changed");
});
ConditionalFlag++;

But to no avail. I have considered using a 25ms timer to check for change like this:

var ConditionalFlag = 0;
function CheckFlag() {
    if (ConditionalFlag > 0) {
        alert("Changed");
        clearInterval(check);
    }
}
var check = window.setInterval("CheckFlag()", 25);
ConditionalFlag++;

However, that seems like overkill. Is there a way to attach an event handler to this variable with jQuery or javascript?

Answer 1

If it's a global variable, you can use property accessors in supported environments...

window._conditional_flag = 0;
Object.defineProperty(window, "ConditionalFlag", {
    get: function() { return window._conditional_flag},
    set: function(v) { console.log("changed"); window._conditional_flag = v; }
});

Answer 2

There's no "event" that gets triggered when a variable changes. JavaScript doesn't work that way.

When does this variable get changed? Just add a call to a function after it does.