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(function($) {
//URI:http://caibaojian.com/scrollfix
//author:caibaojian
//website:http://caibaojian.com
//descirption:scroll and fixed some div
$.fn.scrollFix = function(options) {
return this.each(function() {
var opts = $.extend({}, $.fn.scrollFix.defaultOptions, options);
var obj = $(this),
base = this,
selfTop = 0,
selfLeft = 0,
toTop = 0,
parentOffsetLeft = 0,
parentOffsetTop = 0,
outerHeight,
outerWidth,
objWidth = 0,
placeholder = jQuery('<div>'), //创建一个jquery对象
optsTop = opts.distanceTop, //定义到顶部的高度
endfix = 0; //开始停止固定的位置
var originalPosition;
var originalOffsetTop;
var originalZIndex;
var lastOffsetLeft = -1;
var isUnfixed = true;
//如果没有找到节点，不进行处理
if (obj.length <= 0) {
return;
}
if (lastOffsetLeft == -1) {
originalZIndex = obj.css('z-index');
position = obj.css('position');
originalPosition = obj.css('position');
originalOffsetTop = obj.css('top');
}
var zIndex = obj.css('zIndex');
if (opts.zIndex != 0) {
zIndex = opts.zIndex;
}
//获取相对定位或者绝对定位的父类
var parents = obj.parent();
var Position = parents.css('position');
while (!/^relative|absolute$/i.test(Position)) { //检测浮动元素的父类元素定位为'relative'或者'absolute',是的话退出，否则的话，执行循环，继续寻找它的父类
parents = parents.parent();
Position = parents.css('position');
if (/^body|html$/i.test(parents[0].tagName)) break; //假如父类元素的标签为body或者HTML，说明没有找到父类为以上的定位，退出循环
}
var ie6 = !-[1, ] && !window.XMLHttpRequest; //兼容IE6
var resizeWindow = false;
function resetScroll() {
setUnfixed();
selfTop = obj.offset().top; //对象距离顶部高度
selfLeft = obj.offset().left; //对象距离左边宽度
outerHeight = obj.outerHeight(); //对象高度
outerHeight = parseFloat(outerHeight) + parseFloat(obj.css('marginBottom').replace(/auto/, 0));
outerWidth = obj.outerWidth(); //对象外宽度
// objWidth = obj.width();
objWidth = obj.outerWidth(true);
var documentHeight = $(document).height(); //文档高度
var startTop = $(opts.startTop), //开始浮动固定对象
startBottom = $(opts.startBottom),
toBottom, //停止滚动位置距离底部的高度
ScrollHeight; //对象滚动的高度
//计算父类偏移值
if (/^body|html$/i.test(parents[0].tagName)) { //当父类元素非body或者HTML时，说明找到了一个父类为'relative'或者'absolute'的元素，得出它的偏移高度
parentOffsetTop = 0, parentOffsetLeft = 0;
} else {
parentOffsetLeft = parents.offset().left, parentOffsetTop = parents.offset().top;
}
// 计算父节点的上边到顶部距离
// 如果 body 有 top 属性, 消除这些位移
var bodyToTop = parseInt(jQuery('body').css('top'), 10);
if (!isNaN(bodyToTop)) {
optsTop += bodyToTop;
}
//计算停在底部的距离
if (!isNaN(opts.endPos)) {
toBottom = opts.endPos;
} else {
toBottom = parseFloat(documentHeight - $(opts.endPos).offset().top);
}
//计算需要滚动的高度以及停止滚动的高度
ScrollHeight = parseFloat(documentHeight - toBottom - optsTop), endfix = parseFloat(ScrollHeight - outerHeight);
//计算顶部的距离值
if (startTop[0]) {
var startTopOffset = startTop.offset(),
startTopPos = startTopOffset.top;
selfTop = startTopPos;
}
if (startBottom[0]) {
var startBottomOffset = startBottom.offset(),
startBottomPos = startBottomOffset.top,
startBottomHeight = startBottom.outerHeight();
selfTop = parseFloat(startBottomPos + startBottomHeight);
}
toTop = selfTop - optsTop;
toTop = (toTop > 0) ? toTop : 0;
var selfBottom = documentHeight - selfTop - outerHeight;
//如果滚动停在底部的值不为0，并且自身到底部的高度小于上面这个值，不执行浮动固定
if ((toBottom != 0) && (selfBottom <= toBottom)) {
return;
}
}
function setUnfixed() {
if (!isUnfixed) {
lastOffsetLeft = -1;
placeholder.css("display", "none");
obj.css({
'z-index': originalZIndex,
'width': '',
'position': originalPosition,
'left': '',
'top': originalOffsetTop,
'margin-left': ''
});
obj.removeClass('scrollfixed');
isUnfixed = true;
}
}
function onScroll() {
lastOffsetLeft = 1;
var ScrollTop = $(window).scrollTop();
if (opts.bottom != -1) {
ScrollTop = ScrollTop + $(window).height() - outerHeight - opts.bottom;
}
if (ScrollTop > toTop && (ScrollTop < endfix)) {
if (ie6) { //IE6则使用这个样式
obj.addClass(opts.baseClassName).css({
"z-index": zIndex,
"position": "absolute",
"top": opts.bottom == -1 ? ScrollTop + optsTop - parentOffsetTop : ScrollTop - parentOffsetTop,
"bottom": 'auto',
"left": selfLeft - parentOffsetLeft,
'width': objWidth
})
} else {
obj.addClass(opts.baseClassName).css({
"z-index": zIndex,
"position": "fixed",
"top": opts.bottom == -1 ? optsTop : '',
"bottom": opts.bottom == -1 ? '' : opts.bottom,
"left": selfLeft,
"width": objWidth
});
}
placeholder.css({
'height': outerHeight,
'width': outerWidth,
'display': 'block'
}).insertBefore(obj);
} else if (ScrollTop >= endfix) {
obj.addClass(opts.baseClassName).css({
"z-index": zIndex,
"position": "absolute",
"top": endfix - parentOffsetTop + optsTop,
'bottom': '',
"left": selfLeft - parentOffsetLeft,
"width": objWidth
});
placeholder.css({
'height': outerHeight,
'width': outerWidth,
'display': 'block'
}).insertBefore(obj)
} else {
obj.removeClass(opts.baseClassName).css({
"z-index": originalZIndex,
"position": "static",
"top": "",
"bottom": "",
"left": ""
});
placeholder.remove()
}
}
var Timer = 0;
// if (isUnfixed) {
resetScroll();
// }
$(window).on("scroll", function() {
if (Timer) {
clearTimeout(Timer);
}
Timer = setTimeout(onScroll, 0);
});
// 当发现调整屏幕大小时，重新执行代码
$(window).on("resize", function() {
if (Timer) {
clearTimeout(Timer);
}
Timer = setTimeout(function() {
isUnfixed = false;
resetScroll();
onScroll();
}, 0);
});
})
}
$.fn.scrollFix.defaultOptions = {
startTop: null, //滑到这个位置顶部时开始浮动，默认为空
startBottom: null, //滑到这个位置末端开始浮动，默认为空
distanceTop: 0, //固定在顶部的高度
endPos: 0, //停靠在底部的位置，可以为jquery对象
bottom: -1, //底部位置
zIndex: 0, //z-index值
baseClassName: 'scrollfixed' //开始固定时添加的类
};
})(jQuery);
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