Detect when element is at top

by Jesse M

HTML

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<div id="thing">
this is the element
</div>
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CSS

.fixed {
  position:fixed;
  top:0;
  left:0;
  border:3px solid #000;
}

JavaScript

var distance = $('#thing').offset().top,
    $window = $(window);

$window.scroll(function() {
    if ( $window.scrollTop() >= distance ) {
        // Your div has reached the top
        $('#thing').addClass('fixed');
    }
    if ( $window.scrollTop() < distance ) {
        // Your div has reached the top
        $('#thing').removeClass('fixed');
    }
});