jQuery scroll() detect when user stops scrolling
Ok with this..
$(window).scroll(function()
{
$('.slides_layover').removeClass('showing_layover');
$('#slides_effect').show();
});
I can tell when someone is scrolling from what I understand. So with that I am trying to figure out how to catch when someone has stopped. From the above example you can see I am removing a class from a set of elements while the scrolling is occurring. However, I want to put that class back on when the user stops scrolling.
The reason for this is I am intent on having a layover show while the page is scrolling to give the page a special effect I am attempting to work on. But the one class I am trying to remove while scrolling conflicts with that effect as its a transparency effect to some nature.
Solution 1:
$(window).scroll(function() {
clearTimeout($.data(this, 'scrollTimer'));
$.data(this, 'scrollTimer', setTimeout(function() {
// do something
console.log("Haven't scrolled in 250ms!");
}, 250));
});
Update
I wrote an extension to enhance jQuery's default on-event-handler. It attaches an event handler function for one or more events to the selected elements and calls the handler function if the event was not triggered for a given interval. This is useful if you want to fire a callback only after a delay, like the resize event, or such.
It is important to check the github-repo for updates!
https://github.com/yckart/jquery.unevent.js
;(function ($) {
var on = $.fn.on, timer;
$.fn.on = function () {
var args = Array.apply(null, arguments);
var last = args[args.length - 1];
if (isNaN(last) || (last === 1 && args.pop())) return on.apply(this, args);
var delay = args.pop();
var fn = args.pop();
args.push(function () {
var self = this, params = arguments;
clearTimeout(timer);
timer = setTimeout(function () {
fn.apply(self, params);
}, delay);
});
return on.apply(this, args);
};
}(this.jQuery || this.Zepto));
Use it like any other on or bind-event handler, except that you can pass an extra parameter as a last:
$(window).on('scroll', function(e) {
console.log(e.type + '-event was 250ms not triggered');
}, 250);
http://yckart.github.com/jquery.unevent.js/
(this demo uses resize instead of scroll, but who cares?!)
Solution 2:
Using jQuery throttle / debounce
jQuery debounce is a nice one for problems like this. jsFidlle
$(window).scroll($.debounce( 250, true, function(){
$('#scrollMsg').html('SCROLLING!');
}));
$(window).scroll($.debounce( 250, function(){
$('#scrollMsg').html('DONE!');
}));
The second parameter is the "at_begin" flag. Here I've shown how to execute code both at "scroll start" and "scroll finish".
Using Lodash
As suggested by Barry P, jsFiddle, underscore or lodash also have a debounce, each with slightly different apis.
$(window).scroll(_.debounce(function(){
$('#scrollMsg').html('SCROLLING!');
}, 150, { 'leading': true, 'trailing': false }));
$(window).scroll(_.debounce(function(){
$('#scrollMsg').html('STOPPED!');
}, 150));
Solution 3:
Rob W suggected I check out another post here on stack that was essentially a similar post to my original one. Which reading through that I found a link to a site:
http://james.padolsey.com/javascript/special-scroll-events-for-jquery/
This actually ended up helping solve my problem very nicely after a little tweaking for my own needs, but over all helped get a lot of the guff out of the way and saved me about 4 hours of figuring it out on my own.
Seeing as this post seems to have some merit, I figured I would come back and provide the code found originally on the link mentioned, just in case the author ever decided to go a different direction with the site and ended up taking down the link.
(function(){
var special = jQuery.event.special,
uid1 = 'D' + (+new Date()),
uid2 = 'D' + (+new Date() + 1);
special.scrollstart = {
setup: function() {
var timer,
handler = function(evt) {
var _self = this,
_args = arguments;
if (timer) {
clearTimeout(timer);
} else {
evt.type = 'scrollstart';
jQuery.event.handle.apply(_self, _args);
}
timer = setTimeout( function(){
timer = null;
}, special.scrollstop.latency);
};
jQuery(this).bind('scroll', handler).data(uid1, handler);
},
teardown: function(){
jQuery(this).unbind( 'scroll', jQuery(this).data(uid1) );
}
};
special.scrollstop = {
latency: 300,
setup: function() {
var timer,
handler = function(evt) {
var _self = this,
_args = arguments;
if (timer) {
clearTimeout(timer);
}
timer = setTimeout( function(){
timer = null;
evt.type = 'scrollstop';
jQuery.event.handle.apply(_self, _args);
}, special.scrollstop.latency);
};
jQuery(this).bind('scroll', handler).data(uid2, handler);
},
teardown: function() {
jQuery(this).unbind( 'scroll', jQuery(this).data(uid2) );
}
};
})();
Solution 4:
I agreed with some of the comments above that listening for a timeout wasn't accurate enough as that will trigger when you stop moving the scroll bar for long enough instead of when you stop scrolling. I think a better solution is to listen for the user letting go of the mouse (mouseup) as soon as they start scrolling:
$(window).scroll(function(){
$('#scrollMsg').html('SCROLLING!');
var stopListener = $(window).mouseup(function(){ // listen to mouse up
$('#scrollMsg').html('STOPPED SCROLLING!');
stopListner(); // Stop listening to mouse up after heard for the first time
});
});
and an example of it working can be seen in this JSFiddle
Solution 5:
ES6 style with checking scrolling start also.
function onScrollHandler(params: {
onStart: () => void,
onStop: () => void,
timeout: number
}) {
const {onStart, onStop, timeout = 200} = params
let timer = null
return (event) => {
if (timer) {
clearTimeout(timer)
} else {
onStart && onStart(event)
}
timer = setTimeout(() => {
timer = null
onStop && onStop(event)
}, timeout)
}
}
Usage:
yourScrollableElement.addEventListener('scroll', onScrollHandler({
onStart: (event) => {
console.log('Scrolling has started')
},
onStop: (event) => {
console.log('Scrolling has stopped')
},
timeout: 123 // Remove to use default value
}))