File size: 2,316 Bytes
b3787d8 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 | /*! jQuery.scrollagent (c) 2012, Rico Sta. Cruz. MIT License.
* https://github.com/rstacruz/jquery-stuff/tree/master/scrollagent */
// Call $(...).scrollagent() with a callback function.
//
// The callback will be called everytime the focus changes.
//
// Example:
//
// $("h2").scrollagent(function(cid, pid, currentElement, previousElement) {
// if (pid) {
// $("[href='#"+pid+"']").removeClass('active');
// }
// if (cid) {
// $("[href='#"+cid+"']").addClass('active');
// }
// });
(function($) {
$.fn.scrollagent = function(options, callback) {
// Account for $.scrollspy(function)
if (typeof callback === 'undefined') {
callback = options;
options = {};
}
var $sections = $(this);
var $parent = options.parent || $(window);
// Find the top offsets of each section
var offsets = [];
$sections.each(function(i) {
var offset = $(this).attr('data-anchor-offset') ?
parseInt($(this).attr('data-anchor-offset'), 10) :
(options.offset || 0);
offsets.push({
top: $(this).offset().top + offset,
id: $(this).attr('id'),
index: i,
el: this
});
});
// State
var current = null;
var height = null;
var range = null;
// Save the height. Do this only whenever the window is resized so we don't
// recalculate often.
$(window).on('resize', function() {
height = $parent.height();
range = $(document).height();
});
// Find the current active section every scroll tick.
$parent.on('scroll', function() {
var y = $parent.scrollTop();
y += height * (0.3 + 0.7 * Math.pow(y/range, 2));
var latest = null;
for (var i in offsets) {
if (offsets.hasOwnProperty(i)) {
var offset = offsets[i];
if (offset.top < y) latest = offset;
}
}
if (latest && (!current || (latest.index !== current.index))) {
callback.call($sections,
latest ? latest.id : null,
current ? current.id : null,
latest ? latest.el : null,
current ? current.el : null);
current = latest;
}
});
$(window).trigger('resize');
$parent.trigger('scroll');
return this;
};
})(jQuery);
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