/**
 * JS仿淘宝详情页菜单条智能定位效果
 * constructor SmartFloat * @author tugenhua
 * @time 2014-1-15
 */
 function SmartFloat(options) {
		 this.config = {
		targetElem   :  '#nav'  // 要定位的dom节点
	 };
	 this.cache = {};
	 this.init(options);
 }
 SmartFloat.prototype = {
	constructor: SmartFloat,
	init: function(options){
		//console.log(options);
		this.config = $.extend(this.config, options || {});
		//console.log(this.config);
		var self = this,
			_config = self.config,
			_cache = self.cache;
		//console.log(_config);
		var top = $(_config.targetElem).offset().top,
			pos = $(_config.targetElem).css('position'),
			isIE6 = navigator.userAgent.match(/MSIE 6.0/)!= null;
		$(window).scroll(function(){
			var winTop = $(this).scrollTop();
			if(winTop >= top) {
				if(!isIE6) {
					$(_config.targetElem).css({
						position: 'fixed',
						top: 0
					});
				}else {
					$(_config.targetElem).css({
						position: 'absolute',
						top: winTop
					});
				}
			}else {
				$(_config.targetElem).css({
					position: pos,
					top: top
				});
			}
		});
	}
 };
 // 页面初始化
/*  $(function(){
	 new SmartFloat({
		 });
 }); */