How to clearInterval with unknown ID?

问题:

Say someone (evil) has set us a timer with setInterval, but we don't know its ID (we don't have the reference to the object, that setInterval is returning, nor its value)

(function(){
  setInterval(function(){console.log('pwned')},
              10000)
})();

Is there a way, how to clear it? Is it possible to acces the timer some other way? Or at least in particular browser/javascript engine?

David Flanagan touches similar topic his big JSTDG. setInterval() method, use in malicious code key in the index points to

... Some browsers detect repeated dialog boxes and long-running scripts and give the user the option to stop them. But malicious code can use methods such as setInterval() to load the CPU and can also attack your system by allocating lots of memory. There is no general way that web browsers can prevent this kind of ham-handed attack. In practice, this is not a common problem on the Web since no one returns to a site that engages in this kind of scripting abuse!

回答1:

From quick test, all major browsers (latest Chrome, Firefox and IE) give pretty small numbers as the ID so just looping "blindly" over all possible numbers should work just fine:

function ClearAllIntervals() {
    for (var i = 1; i < 99999; i++)
        window.clearInterval(i);
}

Full example:

window.onload = function() {
    window.setInterval(function() {
        document.getElementById("Tick").innerHTML += "tick<br />";
    }, 1000);
    window.setInterval(function() {
        document.getElementById("Tack").innerHTML += "tack<br />";
    }, 1000);
};

function ClearAllIntervals() {
    for (var i = 1; i < 99999; i++)
        window.clearInterval(i);
}

#Placeholder div { width: 80px; float: left; }

<button type="button" onclick="ClearAllIntervals();">Clear All</button>
<div id="Placeholder">
    <div id="Tick"></div>
    <div id="Tack"></div>
</div>

This will stop all intervals, can't stop specific interval without knowing its ID of course.

As you can test for yourself, it should work on all major browsers mentioned above.

回答2:

Well, empirically trials in Chrome show that setInterval returns a number which increments for each call. So if you are SURE that you setInterval was the last one set the following would work :

function clearLastInterval () {
  var i = setInterval (function () {}, 10000);
  clearInterval (i-1);
  clearInterval (i);
}

I'm not sure I would recommend this though ;-)

回答3:

I tried the approach suggested by #Shadow Wizard and it worked in clearing the interval. However, this approach had side effects afterwards. In my particular case, I was unable use jquery.fadeTo() after clearing all of the intervals.

The approach that I settled on is a cleaner solution, which is to redefine the setInterval method and save the interval ids in the re-defined methods. As shown here, I put the the ids into an array and then clear all of them. With a little more refinement of the structure to store the arrays, you could label them and clear them selectively.

var intervalTracking = new Array();
var intervalCount=0;

window.oldSetInterval = window.setInterval;
window.setInterval = ( function(func, interval) {
    var interval = oldSetInterval(func, interval);
    intervalTracking[++intervalCount]=interval;
    return interval;
});

function clearAllIntervals() {
    for (var i = 0 ; i <= intervalCount ; i++) {
    window.clearInterval( intervalTracking[i] );
    }
}

This seems to work!

回答4:

I solved it by using localstorage, saving there the id of the setInterval, and picking up it later in order to clear that interval..