6

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

omega
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  • The right way seems to be the first piece of code... I don't understand why you want to do this... – elclanrs Mar 10 '16 at 15:27
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    _“except I can't really pass the id value that's returned by the setInterval function, because it gets created after calling it”_ – so what answer besides, “go fire up your time machine!”, do you expect here then …? – CBroe Mar 10 '16 at 15:27
  • … of course you can encapsulate the whole thing into an object (if you’re opposed to having a _global_ variable holding the interval id laying around.) – CBroe Mar 10 '16 at 15:28
  • You don't want to reference the variable from outside -> that's how it was designed you have no choice see http://www.w3schools.com/jsref/met_win_clearinterval.asp. – Walfrat Mar 10 '16 at 15:31

2 Answers2

5

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");
T.J. Crowder
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0

You can create a new method, which can provide you the desired functionality, like 

window.createInterval = function(cb, timeout, data) {
  if (typeof cb !== "function") {
    throw new Error("Please provide a callback.");
  }

  var interval = window.setInterval(function(data) {
    cb(data, interval);
  }, timeout || 0, data);

  return interval;
};

Now this works like

var myInterval = window.createInterval(function(data, interval){
  console.log(data, interval);
}, 1000, "Hello");

which prints Hello and Interval Id (same as myInterval)

window.createInterval = function(cb, timeout, data) {
  if (typeof cb !== "function") {
    throw new Error("Please provide a callback.");
  }

  var interval = window.setInterval(function(data) {
    cb(data, interval);
  }, timeout || 0, data);

  return interval;
};

var myInterval = window.createInterval(function(data, interval) {
  document.write(data + " " + interval + " " + myInterval);
  window.clearInterval(interval);
}, 1000, "Hello");
Ammar Hasan
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