JS 鼠标按下 onmousedown onmouseup

<div style="width:300px;height:300px;background:#456"></div>
var div = document.getElementsByTagName('div')[0];

//绑定事件
div.onmousedown = function() {
    alert('鼠标被按下了啊!!!');
}

div.onmouseup = function() {
    alert('鼠标被抬起来了!!!!');
}