$.fn.initScroll = function(){
  this.each(function(){
  
  	//创建包含内容的容器
	$(this).wrapInner("<div class='\"scrollContent\"'></div>");
	var $scrollContent = $(this).find(".scrollContent");
	
	var contentHeight = $scrollContent.height();
	var wrapperHeight = $(this).height();
	if(contentHeight &gt; wrapperHeight){
		//创建滚动条
		var $_scrollBarContainer = $("<div class='\"scrollBarContainer\"'></div>");
		var $_scrollBarBlock = $("<div class='\"scrollBarBlock\"'></div>");
		$_scrollBarBlock.css("opacity","0.5");
		$_scrollBarContainer.append($_scrollBarBlock);
		$(this).append($_scrollBarContainer);
		//定义滚动条相关变量
		var $scrollBarContainer = $(this).find(".scrollBarContainer");
		var $scrollBarBlock = $(this).find(".scrollBarBlock");
		//留出滚动条的位置
		$scrollContent.css("padding-right", "36px");
		//重新计算内容高度
		contentHeight = $(this).find(".scrollContent").height();
		//计算滑块大小
		var scrollBarBlockHeight = wrapperHeight * $(this).find(".scrollBarContainer").height() / contentHeight;
		//设置滑块大小
		//$scrollBarBlock.css("height",scrollBarBlockHeight);
		$scrollBarBlock.css("height",scrollBarBlockHeight);
		//滚动条滑块效果
		$scrollBarBlock.hover(function(){
				$(this).stop(true,true).animate({"opacity":"1"});
			},function(){
				$(this).stop(true,true).animate({"opacity":"0.5"});
			});
		//计算滑块可拖动距离
		var scrollMaxLength = $(this).find(".scrollBarContainer").height() - scrollBarBlockHeight;
		//超出容器的内容高度
		var scrollContentLength = contentHeight - wrapperHeight;
		//内容滚动比例 每一像素滚动条
		var d = scrollContentLength/scrollMaxLength;
		
		//滚动效果
		//是否开始滚动
		var start = false;
		//滚动条开始滚动时的位置
		var scrollStartY = 0;
		//鼠标按下时候的位置
		var mouseStartY = 0;
		//鼠标拖动时的即时位置
		var mouseMovingY = 0;
		
		$scrollBarBlock.mousedown(function(event){
			event.preventDefault();
			mouseStartY = event.pageY;
			scrollStartY = $scrollBarBlock.position().top;
			start = true;
		});
		//防止鼠标拖出滑块的位置失效，一下方法针对document
		$(document).mouseup(function(){
			//停止滚动
			start = false;
			//滚动条样式效果
			$scrollBarBlock.stop(true,true).animate({"opacity":"0.5"});
		}).mousemove(function(event){
			event.preventDefault();
			if(start){
				mouseMovingY = event.pageY;
				//计算滚动条要移动的距离，即鼠标移动的距离
				var scrollLength = mouseMovingY - mouseStartY;
				//滚动条滚动的顶部即时位置
				var scrollCurrentY = scrollStartY + scrollLength;
				if(scrollCurrentY &lt; 0){
					scrollCurrentY = 0;
				}else if(scrollCurrentY &gt; scrollMaxLength){
					scrollCurrentY = scrollMaxLength;
				}
				//设置滚动条即时位置及效果
				$scrollBarBlock.stop(true,true).css({"top":scrollCurrentY, "opacity":"1"});
				
				//计算内容滚动的即时值
				var contentCurrentY = scrollCurrentY * d;
				//设置内容滚动即时值
				$scrollContent.css("margin-top", -contentCurrentY);
				
			}
		});
		
		//鼠标滚轮
		$(".scrollBar").mousewheel(function(event, delta){
			event.preventDefault();
			//每次滚动内容的偏移量
			var wheelLength = 24;
			//内容滚动时的初始值
			var contentStartY = parseFloat($scrollContent.css("margin-top"));
			//console.log(contentStartY);
			//比例
			var d = scrollMaxLength/scrollContentLength;
			if(delta &lt; 0){
				//滚动滚轮一次后的内容偏移量
				var wheelContentY = contentStartY - 24;
				if(wheelContentY &lt; -scrollContentLength){
					wheelContentY = -scrollContentLength;
				}
			}else if(delta &gt; 0){
				//滚动滚轮一次后的内容偏移量
				var wheelContentY = contentStartY + 24;
				if(wheelContentY &gt; 0){
					wheelContentY = 0;
				}	
			}
			//设置内容偏移量
			$scrollContent.css("margin-top", wheelContentY);
				//计算滚动条的偏移量
			var wheelScrollY = -wheelContentY * d;
				//滚动条初始位置
			var wheelScrollStartY = parseFloat($scrollBarBlock.css("margin-top"));
				//滚动条的偏移位置
			var scrollCurrentY = wheelScrollY + wheelScrollStartY;
				//设置滚动条偏移量
			$scrollBarBlock.css("top", scrollCurrentY);
		});
		
		
	}
  
  });
}