鼠标悬停(鼠标悬停一段时间后触发事件)一段时间后触发事件，鼠标停留超过N秒,才触发

<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<script type="text/javascript">
    var mytimer = null;
   
    function beginEvent(){     
      //window.setTimeout("alert('Hello, world')", 1000);
      mytimer = window.setTimeout("myfunc('123','456')", 3000);        
    }

    

function cancelEvent() {
  clearTimeout(mytimer);      
  mytimer = -1;
}

function myfunc(t1,t2) {
                alert(t1+" ,"+t2);
        if (mytimer == -1) return;
        var d = document.getElementById("div1");
        d.innerText = new Date();
        clearTimeout(mytimer);
        mytimer = null;
}
</script>
</head>
<body>
  <br/>
  <br/>
  <div id="div1" style="position: absolute; top: 100px; left: 100px;  100px; height: 100px; border: 1px solid black;" onmouseover="beginEvent()" onmouseout="cancelEvent()"></div>
</body>
</html>

//鼠标放上去0.5秒后执行preview方法，鼠标移出就清除timeout
$('body').on('mouseover','.ac_over',function() {
        timer = setTimeout(function(){
            preview($('.ac_over').attr('data-id'));
        },500);
    });
    $('body').on('mouseout','.ac_over',function() {
        clearTimeout(timer);
    });