Scroll event firing too many times. I only want it to fire a maximum of, say, once per second

Question

I have a page with \"infinite scroll\". It calculates the difference between the end of the page and the current page and loads more content if this difference is small enou

Answer 1

Here is a solution that doesn't require the use of an extra JS library or plugin, that aims for simplicity. It might not be as efficient as other implementations but it is definitely a step up from firing your main event every time you scroll.

This was taken from this blog post by Danny Van Kooten. Which I have used in delaying my onscroll() events for my back-to-top button on my blog.

var timer;
$(window).scroll(function() {
    if(timer) {
        window.clearTimeout(timer);
    }
    timer = window.setTimeout(function() {
       // actual code here. Your call back function.
    console.log( "Firing!" );
    }, 100);
});

You can also further improve performance by moving out variables out of the callback function to avoid unnecessary recalculations, for example the value of $(window).height() or height of some static div element that won't change once the page is loaded.

Here's an example that is adapted from my use case.

var scrollHeight = $("#main-element").height(); //never changes, no need to recalculate.
$(window).on('scroll', function() {
    if (timer) 
        window.clearTimeout(timer);
    timer = window.setTimeout(function() {
        var scrollPosition = $(window).height() + $(window).scrollTop();    
        if ($(window).scrollTop() < 500)
            $(".toggle").fadeIn(800);
        else 
            $(".toggle").fadeOut(800);
    }, 150); //only fire every 150 ms.
});

This limits the actual function to only execute every 150ms, or else reset the timer back to 0 if 150ms has not passed. Tweak the value to suit what you need.

Answer 2

the scroll fire multiple times is correct and you should able to get the scroll position differently each time. I think you need to set a timer when you first get in the scroll event like you mentioned x milliseconds, and also record the time stamp, and then next time scroll event fire, check the last trigger time and ignore it if it's within x milliseconds, and do the real job in your Timer action.