window.scroll events triggering twice

Question

No matter what method I use to detect scrolling on the page the event is triggered twice. Please see the code for the different methods I have tried.

<body onmousewheel="alert('Why are you alerting twice?')">

or

<script src="js/jquery-1.8.3.min.js"></script> <script> $(window).scroll(function(){ alert("Why are you alerting twice?"); }); </script>

or

window.onscroll = please_scroll; function please_scroll() { alert("Why are you alerting twice?"); }

I have even tried using $.debounce.

In case it is of any use I will explain what I am trying to do: When the user scrolls the wheel either up or down, the page will animate the scroll to the next full width content div. I have code that is successfully doing this onclick of my menu, but I would also like it to happen as the user scrolls, essentially auto assisting them with scrolling to each part of my page. This is the function I currently have for scrolling:

function scrollTo(id){ // Scroll $('html,body').animate({scrollTop: $("#"+id).offset().top - 110},'slow',function(){ animation_active = "false"; }); }

firstly, should be: window.onscroll = please_scroll; Secondly, you shouldn't use alert to debug event — A. Wolff
– A. Wolff, Commented Feb 25, 2014 at 15:17
well the mousewheel and other hids like the apple mouses can trigger scroll events more often when being used. you have to use a timeout for that — Alex
– Alex, Commented Feb 25, 2014 at 15:20

Alex · Accepted Answer · 2014-02-25 15:22:56Z

19

many devices can trigger scroll events which appear to happen once more often. simply use a timeout for that:

var timeout; $(window).scroll(function() { clearTimeout(timeout); timeout = setTimeout(function() { // do your stuff }, 50); });

you can play with the value 50, i recommend something between 50 and 150.

answered Feb 25, 2014 at 15:22

Alex

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4 Comments

Iceman3000 Over a year ago

I just spent 4 hours trying to debug this and you seem to have resolved my issues straight up. Wow. Thanks!

Leon Gaban Over a year ago

LOL me too! I did not think a timeout would be needed, my question: stackoverflow.com/questions/32383804/…

WantToDo Over a year ago

Working but with delay!, not immediate

Alex Over a year ago

@WantToDo decrease the 50 to whatever floats your boat

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