How to get the number of pixels a user has scrolled down the page?

In pure javascript you can simply do like that:

window.onscroll = function (e) {
    console.log(window.scrollY); // Value of scroll Y in px
};

More infos (The Mozilla Developer Network) :

• onscroll
• scrollY

This is what i used on my website… when anyone scrolls 620 pixels down the menu will pop up, I input the numbers manually. I’m still a noob at javascript but I hope this helps

    <script>
    $(document).ready(function(){
        $(window).scroll(function(){
            var scrollTop = 620;
            if($(window).scrollTop() >= scrollTop){
                $('.Nav').css({
                    position : 'fixed',
                    top : '0'
                });
            }
            if($(window).scrollTop() < scrollTop){
                $('.Nav').removeAttr('style');  
            }
        })
    })
    </script>

Yes. See scrollTop() in jQuery, which wraps the scrollTop DOM property.

You can use window.scrollX to detect how much pixels the user has scrolled right.
You can use window.scrollY to detect how much pixels the user has scrolled down.
You can use window.scrollTo(x, y); to set scroll pixels right (x) and down (y).

Example code:

var x = window.scrollX, y = window.scrollY;
window.scrollTo(0, 200);

This will work fine in chrome

window.addEventListener('scroll', function() {
    console.log(scrollY);
});