Snap To Top of Div/Element on Scroll

Question

Can anyone recommend a "best" approach for snapping the scrollbar to the top of an element when scrolling down a page?

For example, if my layout was as follows:

<div id="section-one" style="width: 100%; height: 600px;">
    Section One
</div>

<div id="section-two" style="width: 100%; height: 600px;">
    Section Two
</div>

<div id="section-three" style="width: 100%; height: 600px;">
    Section Three
</div>

<div id="section-four" style="width: 100%; height: 600px;">
    Section Four
</div>

If the user was viewing section one and began browsing down with section two beginning to take part of the browser viewport, I'd like the browser to automatically snap to the top of the next div.

I'm familiar with .scroll() and .scrollTop but a little unsure with where to go from here.

Answer 1

What you could do is set

body {
overflow:hidden
}

and have control on user interactions, let's say you have a menu if user selects a section in the menu you just animate with scrollTop to redirect to the section.

Another solution, since you have a defined height which is 600px you could calculate with scrollTop and scroll where the user is located in the document something like this...

$(window).scroll(function () { 
      console.log($(window).scrollTop());
});​

Example: http://jsfiddle.net/3STQN/

Answer 2

If multiple divs can get into the view, then you can change the function isScrolledIntoView to, let's say, isTopInTheView, or something similar. In that function you can check if the top of the div is visible, and if it is, snap that div to the top of the screen.

EDIT: and, of course, once you find the first div that fulfills the requirements, just return from the function so it can't check any more divs.

Answer 3

you can check if element is in wiewport with this isScrolledIntoView function created by @Scott Dowding,

And here is an example,

$(document).scroll(function() {
    $("div:not(.highlight)").each(function() {
        if (isScrolledIntoView(this)) {
           $("div").removeClass("highlight");
           $(this).addClass("highlight");
           $("body").animate({ scrollTop: $(this).offset().top }, 1000)
        }
    });
});

function isScrolledIntoView(elem)
{
    var docViewTop = $(window).scrollTop();
    var docViewBottom = docViewTop + $(window).height();

    var elemTop = $(elem).offset().top;
    var elemBottom = elemTop + $(elem).height();

    return (elemTop <= docViewBottom) && (elemTop > docViewTop);
}​

DEMO