文本框中的文本自动滚动的效果

JS

window.onload = function(){
	var rollContent = document.getElementById("rollContent"),//获取元素
			_div = rollContent.innerHTML,
			setCss = function(_this, cssOption){//设置样式
				if ( !_this || _this.nodeType === 3 || _this.nodeType === 8 || !_this.style ) {
					return;
				}
				for(var cs in cssOption){
					_this.style[cs] = cssOption[cs];
				}
				return _this;
			};
	rollContent.innerHTML = "<div id='rollContent_roll'>"+_div+"</div>";
	setCss(rollContent, {//初始化样式
		"position":"relative",
		"overflow":"hidden",
		"wordWrap":"break-word",
		"wordBreak":"break-all",
		"width":rollContent.getAttribute("data-rwidth"),
		"height":rollContent.getAttribute("data-rhight")
	});

	var timeRoll = document.getElementById("rollContent_roll"),
			_h = timeRoll.offsetHeight;
			timeoutRoll = function(){//修改top值
				var _h = timeRoll.offsetHeight,
						_t = parseInt(timeRoll.style.top, 10),
						_tt =  _h > Math.abs(_t) || _t >= 0 ? _t-10: (_h || 0);//是否将top设置为0
				setCss(timeRoll, {
					"top":_tt+"px"
				});
				setTimeout(timeoutRoll,200);//间时调用，模拟动画
			};

	if(_h > rollContent.getAttribute("data-rhight")){
		timeoutRoll();
		setCss( timeRoll, {
			"position":"relative",
			"top":"0px"
		});
	}

};