How to pass intervalID to interval function in javascript?

Question

In javascript when I create an interval, I want to stop the interval from inside the function, but I don't want to reference the ID value from outside like this

var y = setInterval(function(){ clearInterval(y); }, 1000);

What I want is to pass a variable similar to this style

setTimeout(function(data){alert(data);}, 1000, "data");

This works for setInterval too, except I can't really pass the id value that's returned by the setInterval function, because it gets created after calling it.

Right now I'm doing a hack like this:

var r = [];
var y = setInterval(function(r){ if (r.length==1) { clearInterval(r[0]); } }, 1000, r);
r.push(y);

Does anyone know the right way?

Thanks

Answer 1

You have to use the return value, but that doesn't mean that the variable needs to be accessible to anything else; just encapsulate:

(function() {
    var y = setInterval(function(){ clearInterval(y); }, 1000);
})();

y in the above is only accessible within the outer anonymous function, which only has the interval function and nothing else in it.

You could even give yourself a reusable setInterval wrapper to do it:

function setIntervalWrapper(callback, time) {
    var args = Array.prototype.slice.call(arguments, 1);
    args[0] = setInterval(function() {
        callback.apply(null, args);
    }, time);
}

That will pass the time handle as the first argument, in front of any others you specify. It also has the benefit of supporting those follow-on arguments reliably cross-browser (some older browsers didn't support passing arguments to the callback).

Gratuitous example:

function setIntervalWrapper(callback, time) {
    var args = Array.prototype.slice.call(arguments, 1);
    args[0] = setInterval(function() {
        callback.apply(null, args);
    }, time);
}

var counter = 0;
setIntervalWrapper(function(handle, arg1, arg2) {
    console.log("Interval callback called, handle is " + handle + ", args are '" + arg1 + "' and '" + arg2 + "'");
    if (++counter > 5) {
        console.log("counter > 5, stopping");
        clearInterval(handle);
    }
}, 500, "a", "b");