判断鼠标是否在指定区域代码

<div style="300px; height:300px; border:1px solid red;">
　　<div id="target"><div><span>测试</span></div></div>
</div>

<style type="text/css">
#target{  200px; height: 200px; background: #EEE;}
#target div{ 150px; height: 150px; border:1px solid orange;}
#target span{ display: block;  50px; height: 50px; background: gray;}
</style>

var target = document.getElementById('target');
	if(target.addEventListener){
		target.addEventListener("mouseout",mouseoutHander,false)
	}else if(target.attachEvent){
		target.attachEvent("onmouseout",mouseoutHander);
	}else{
		target.onmouseout = mouseoutHander;
	}
	function mouseoutHander(e){
		e = e || window.event;
		var target = e.target || e.srcElement;

		  // 判断移出鼠标的元素是否为目标元素
		  if (target.id !== 'target') {
		    return;
		  }

		  // 判断鼠标是移出元素还是移到子元素
		  var relatedTarget = e.relatedTarget || e.toElement;
		  while (relatedTarget !== target
		    && relatedTarget.nodeName.toUpperCase() !== 'BODY') {
		    relatedTarget = relatedTarget.parentNode;
		  }

		  // 如果相等，说明鼠标在元素内部移动
		  if (relatedTarget === target) {
		    return;
		  }

		  // 执行需要操作
		  alert('鼠标移出');
	}

执行以上代码，鼠标在指定区域移动就不会一直弹出警告框