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September 16, 2014 22:44
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jquery.parallax
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| /************************* | |
| *---JQUERY PARALLAX---- * | |
| ************************* | |
| * | |
| * Alexander Junger, 2014 | |
| * License: MIT | |
| * | |
| */ | |
| (function($) { | |
| 'use strict'; | |
| var DEFAULT_CONFIG = { | |
| minWidth: 780 | |
| }; | |
| var $window = $(window), | |
| $body = $('body'), | |
| $document = $(document); | |
| var elements = []; | |
| window.elements = elements; | |
| var Parallax = function($el, config) { | |
| if(!$el.length) { | |
| return; | |
| } | |
| this.$el = $el; | |
| this.c = $.merge(config, {minOff: 0, maxOff: $document.height(), speed: 0.1}); | |
| this.speed = parseFloat(this.c.speed); | |
| this.originalOffset = parseInt(this.$el.css('top'), 10); | |
| elements.push(this); | |
| }; | |
| Parallax.prototype.update = function() { | |
| if(this.isVisible()) { | |
| this.$el.css('top', this.getOffset.bind(this)); | |
| } | |
| }; | |
| Parallax.prototype.isVisible = function() { | |
| var docTop = $window.scrollTop(); | |
| var docBottom = docTop + $window.height(); | |
| var elemTop = this.$el.offset().top; | |
| var elemBottom = elemTop + this.$el.height(); | |
| return ((elemBottom >= docTop) && (elemTop - 400 <= docBottom)); | |
| }; | |
| Parallax.prototype.getOffset = function() { | |
| var rawOffset = this.originalOffset - $window.scrollTop() * this.speed * 0.05; | |
| return Math.max(0, Math.min(rawOffset)); | |
| }; | |
| var updateAll = function() { | |
| $body.css({ | |
| 'background-position': 'center -' + $window.scrollTop() * 0.15 + 'px' | |
| }); | |
| elements.forEach(function(p) { | |
| p.update(); | |
| }); | |
| }; | |
| $window.on('scroll', updateAll); | |
| $.fn.parallax = function() { | |
| if($window.width() <= DEFAULT_CONFIG.minWidth) { | |
| return false; | |
| } | |
| this.each(function() { | |
| $(this).data('parallaxObject', new Parallax($(this), { | |
| speed: parseFloat($(this).data('parallax-speed')) | |
| })); | |
| }); | |
| return this; | |
| }; | |
| })(jQuery); |
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