jQuery-viewport-checker see description link
此脚本不应直接安装。它是供其他脚本使用的外部库，要使用该库请加入元指令 // @require https://update.gf.qytechs.cn/scripts/7702/33495/jQuery-viewport-checker.js
/*
Version 1.7.4
The MIT License (MIT)
Copyright (c) 2014 Dirk Groenen
Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
*/
(function($){
$.fn.viewportChecker = function(useroptions){
// Define options and extend with user
var options = {
classToAdd: 'visible',
classToRemove : 'invisible',
offset: 100,
repeat: false,
invertBottomOffset: true,
callbackFunction: function(elem, action){},
scrollHorizontal: false
};
$.extend(options, useroptions);
// Cache the given element and height of the browser
var $elem = this,
windowSize = {height: $(window).height(), width: $(window).width()},
scrollElem = ((navigator.userAgent.toLowerCase().indexOf('webkit') != -1) ? 'body' : 'html');
/*
* Main method that checks the elements and adds or removes the class(es)
*/
this.checkElements = function(){
var viewportStart, viewportEnd;
// Set some vars to check with
if(!options.scrollHorizontal){
viewportStart = $(scrollElem).scrollTop();
viewportEnd = (viewportStart + windowSize.height);
}
else{
viewportStart = $(scrollElem).scrollLeft();
viewportEnd = (viewportStart + windowSize.width);
}
// Loop through all given dom elements
$elem.each(function(){
var $obj = $(this),
objOptions = {},
attrOptions = {};
// Get any individual attribution data
if ($obj.data('vp-add-class'))
attrOptions.classToAdd = $obj.data('vp-add-class');
if ($obj.data('vp-remove-class'))
attrOptions.classToRemove = $obj.data('vp-remove-class');
if ($obj.data('vp-offset'))
attrOptions.offset = $obj.data('vp-offset');
if ($obj.data('vp-repeat'))
attrOptions.repeat = $obj.data('vp-repeat');
if ($obj.data('vp-scrollHorizontal'))
attrOptions.scrollHorizontal = $obj.data('vp-scrollHorizontal');
if ($obj.data('vp-invertBottomOffset'))
attrOptions.scrollHorizontal = $obj.data('vp-invertBottomOffset');
// Extend objOptions with data attributes and default options
$.extend(objOptions, options);
$.extend(objOptions, attrOptions);
// If class already exists; quit
if ($obj.hasClass(objOptions.classToAdd) && !objOptions.repeat){
return;
}
// define the top position of the element and include the offset which makes is appear earlier or later
var elemStart = (!objOptions.scrollHorizontal) ? Math.round( $obj.offset().top ) + objOptions.offset : Math.round( $obj.offset().left ) + objOptions.offset,
elemEnd = (!objOptions.scrollHorizontal) ? elemStart + $obj.height() : elemStart + $obj.width();
if(objOptions.invertBottomOffset)
elemEnd -= (objOptions.offset * 2);
// Add class if in viewport
if ((elemStart < viewportEnd) && (elemEnd > viewportStart)){
// remove class
$obj.removeClass(objOptions.classToRemove);
$obj.addClass(objOptions.classToAdd);
// Do the callback function. Callback wil send the jQuery object as parameter
objOptions.callbackFunction($obj, "add");
// Remove class if not in viewport and repeat is true
} else if ($obj.hasClass(objOptions.classToAdd) && (objOptions.repeat)){
$obj.removeClass(objOptions.classToAdd);
// Do the callback function.
objOptions.callbackFunction($obj, "remove");
}
});
};
// Run checkelements on load and scroll
$(window).bind("load scroll touchmove MSPointerMove", this.checkElements);
// On resize change the height var
$(window).resize(function(e){
windowSize = {height: $(window).height(), width: $(window).width()},
$elem.checkElements();
});
// trigger inital check if elements already visible
this.checkElements();
// Default jquery plugin behaviour
return this;
};
})(jQuery);