(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();
				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);