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.

Solution

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

Comments

[Okan Kocyigit]

yes, because isScrolledIntoView returns true if element in wiewport, I've changed the function, that's seems working now as you say.

[cqde]

Awesome. I guess the only thing that causes some buggy business is when the viewport shows more than one div, which causes JS to add/remove the "highlight" class multiple times to the different divs that are present. I might try finding a way to check if a div has a majority of window real estate or maybe have each div elastic, with 100% width AND height?