js/scrollspy.js
/**
* Extend jquery with a scrollspy plugin.
* This watches the window scroll and fires events when elements are scrolled into viewport.
*
* throttle() and getTime() taken from Underscore.js
* https://github.com/jashkenas/underscore
*
* @author Copyright 2013 John Smart
* @license https://raw.github.com/thesmart/jquery-scrollspy/master/LICENSE
* @see https://github.com/thesmart
* @version 0.1.2
*/
(function($) {
var jWindow = $(window);
var elements = [];
var elementsInView = [];
var isSpying = false;
var ticks = 0;
var unique_id = 1;
var offset = {
top : 0,
right : 0,
bottom : 0,
left : 0,
}
/**
* Find elements that are within the boundary
* @param {number} top
* @param {number} right
* @param {number} bottom
* @param {number} left
* @return {jQuery} A collection of elements
*/
function findElements(top, right, bottom, left) {
var hits = $();
$.each(elements, function(i, element) {
if (element.height() > 0) {
var elTop = element.offset().top,
elLeft = element.offset().left,
elRight = elLeft + element.width(),
elBottom = elTop + element.height();
var isIntersect = !(elLeft > right ||
elRight < left ||
elTop > bottom ||
elBottom < top);
if (isIntersect) {
hits.push(element);
}
}
});
return hits;
}
/**
* Called when the user scrolls the window
*/
function onScroll(scrollOffset) {
// unique tick id
++ticks;
// viewport rectangle
var top = jWindow.scrollTop(),
left = jWindow.scrollLeft(),
right = left + jWindow.width(),
bottom = top + jWindow.height();
// determine which elements are in view
var intersections = findElements(top+offset.top + scrollOffset || 200, right+offset.right, bottom+offset.bottom, left+offset.left);
$.each(intersections, function(i, element) {
var lastTick = element.data('scrollSpy:ticks');
if (typeof lastTick != 'number') {
// entered into view
element.triggerHandler('scrollSpy:enter');
}
// update tick id
element.data('scrollSpy:ticks', ticks);
});
// determine which elements are no longer in view
$.each(elementsInView, function(i, element) {
var lastTick = element.data('scrollSpy:ticks');
if (typeof lastTick == 'number' && lastTick !== ticks) {
// exited from view
element.triggerHandler('scrollSpy:exit');
element.data('scrollSpy:ticks', null);
}
});
// remember elements in view for next tick
elementsInView = intersections;
}
/**
* Called when window is resized
*/
function onWinSize() {
jWindow.trigger('scrollSpy:winSize');
}
/**
* Enables ScrollSpy using a selector
* @param {jQuery|string} selector The elements collection, or a selector
* @param {Object=} options Optional.
throttle : number -> scrollspy throttling. Default: 100 ms
offsetTop : number -> offset from top. Default: 0
offsetRight : number -> offset from right. Default: 0
offsetBottom : number -> offset from bottom. Default: 0
offsetLeft : number -> offset from left. Default: 0
activeClass : string -> Class name to be added to the active link. Default: active
* @returns {jQuery}
*/
$.scrollSpy = function(selector, options) {
var defaults = {
throttle: 100,
scrollOffset: 200, // offset - 200 allows elements near bottom of page to scroll
activeClass: 'active',
getActiveElement: function(id) {
return 'a[href="#' + id + '"]';
}
};
options = $.extend(defaults, options);
var visible = [];
selector = $(selector);
selector.each(function(i, element) {
elements.push($(element));
$(element).data("scrollSpy:id", i);
// Smooth scroll to section
$('a[href="#' + $(element).attr('id') + '"]').click(function(e) {
e.preventDefault();
var offset = $(Materialize.escapeHash(this.hash)).offset().top + 1;
$('html, body').animate({ scrollTop: offset - options.scrollOffset }, {duration: 400, queue: false, easing: 'easeOutCubic'});
});
});
offset.top = options.offsetTop || 0;
offset.right = options.offsetRight || 0;
offset.bottom = options.offsetBottom || 0;
offset.left = options.offsetLeft || 0;
var throttledScroll = Materialize.throttle(function() {
onScroll(options.scrollOffset);
}, options.throttle || 100);
var readyScroll = function(){
$(document).ready(throttledScroll);
};
if (!isSpying) {
jWindow.on('scroll', readyScroll);
jWindow.on('resize', readyScroll);
isSpying = true;
}
// perform a scan once, after current execution context, and after dom is ready
setTimeout(readyScroll, 0);
selector.on('scrollSpy:enter', function() {
visible = $.grep(visible, function(value) {
return value.height() != 0;
});
var $this = $(this);
if (visible[0]) {
$(options.getActiveElement(visible[0].attr('id'))).removeClass(options.activeClass);
if ($this.data('scrollSpy:id') < visible[0].data('scrollSpy:id')) {
visible.unshift($(this));
}
else {
visible.push($(this));
}
}
else {
visible.push($(this));
}
$(options.getActiveElement(visible[0].attr('id'))).addClass(options.activeClass);
});
selector.on('scrollSpy:exit', function() {
visible = $.grep(visible, function(value) {
return value.height() != 0;
});
if (visible[0]) {
$(options.getActiveElement(visible[0].attr('id'))).removeClass(options.activeClass);
var $this = $(this);
visible = $.grep(visible, function(value) {
return value.attr('id') != $this.attr('id');
});
if (visible[0]) { // Check if empty
$(options.getActiveElement(visible[0].attr('id'))).addClass(options.activeClass);
}
}
});
return selector;
};
/**
* Listen for window resize events
* @param {Object=} options Optional. Set { throttle: number } to change throttling. Default: 100 ms
* @returns {jQuery} $(window)
*/
$.winSizeSpy = function(options) {
$.winSizeSpy = function() { return jWindow; }; // lock from multiple calls
options = options || {
throttle: 100
};
return jWindow.on('resize', Materialize.throttle(onWinSize, options.throttle || 100));
};
/**
* Enables ScrollSpy on a collection of elements
* e.g. $('.scrollSpy').scrollSpy()
* @param {Object=} options Optional.
throttle : number -> scrollspy throttling. Default: 100 ms
offsetTop : number -> offset from top. Default: 0
offsetRight : number -> offset from right. Default: 0
offsetBottom : number -> offset from bottom. Default: 0
offsetLeft : number -> offset from left. Default: 0
* @returns {jQuery}
*/
$.fn.scrollSpy = function(options) {
return $.scrollSpy($(this), options);
};
})(jQuery);