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how to alert if user scrolls down the page?
Posted: Wed Apr 28, 2010 2:21 am
by eshban
Hi,
Can anyone please tell me that
" how to write a JavaScript function to pop up an alert() if a user scrolls down the webpage faster than a certain speed"
Looking forward for a urgent reply
Thanks
Re: how to alert if user scrolls down the page?
Posted: Wed Apr 28, 2010 12:17 pm
by kaszu
If some website would not allow me to scroll as fast as I want (even for T&C) I would leave immediately. But here it is:
Code: Select all
var max_px_per_second = 1000;
var last_pos = 0;
var prev_pos = null;
//Check every 250ms if user has scrolled more than max_px_per_second/4 pixels
setInterval(function () {
var dif = Math.abs(last_pos - prev_pos);
if (dif > max_px_per_second / 4) {
alert('LIMITING USER IS EVIL AND REALLY SHOULDN\'T BE DONE!');
}
prev_pos = last_pos;
}, 250);
window.onscroll = function () {
var pos = window.scrollY || window.pageYOffset || document.body.parentElement.scrollTop;
//Save scroll position
last_pos = pos;
//Make sure popup doesn't appear after page refresh
if (prev_pos === null) prev_pos = last_pos;
};
Can you tell us why you need this (since I wrote code for you)?