请教大神让js鼠标放上去固定，移开自动切换

<script type="text/javascript">
   
   
   
    var tt
   
        function changeShow(num) {
        
            
            number=num
            number++;
            if(number>3){
            number=1;
            }
            
            for (var i = 1; i < 4; i++) {
                    document.getElementById("liTitle" + i).className = "off";
                    document.getElementById("ulcontent" + i).style.display = "none";
            }
            
            document.getElementById("liTitle" + num).className = "on";
            document.getElementById("ulcontent" + num).style.display = "block";
        }
        var number=1
        
        
        $(function(){
            
        
        tt=setInterval(function(){
        changeShow(number)
        },2000)
        
        })
    </script>