Check if a timeout is waiting to run?

Question

I have an infinity scroll style page I'm working on, (for an example of infinity scroll, click here and scroll down) which runs a function called `update()` every time the user scrolls, among other things. I could use `setInterval` instead and check every x millis, however with a timeout that calls itself, the page responds quicker and more reliably. Basically, `update()` adds some content to the page, then, if that content isn't enough to let you scroll down more, sets a timeout to call `update()` again. If you only scrolled one pixel, this would be fine, but of course, when you scroll it sends tens or hundreds of scroll events. This becomes a problem because there will be tens (or hundreds) of timeouts running at once. Having too many timeouts kills the consistent animation of adding new content I was going for. So I wanted to check for if a timeout was already waiting to execute using the ID I had, however there doesn't seem to be a function for this is JavaScript. Is there a way t…

Accepted Answer

When the function fires, clear the interval and set the variable you're holding the initial in to null. Then check for a null value. If you're doing a bunch of these, you could store them in an array by the id you have.

eg:

```
var intervals = [];

if(intervals[id] != null){
    intervals[id] = setTimeout(some_func, 1000);

var some_func = function(){
        // do stuff
        clearTimeout(intervals[id]);
        intervals[id] = null;
    }
}
```

Check if a timeout is waiting to run?

Solution

Problem