<div id="box"></div>

<style>        #box{            width: 300px;            height: 200px;            background-color: skyblue;            position: absolute;            left: -250px;            top: 0;            cursor: pointer;        }    </style>

<script>            window.onload=function(){                var box=document.getElementById("box");                var box_left=-250;                var times;                var back_times;                box.onmouseover=function(){                    clearInterval(back_times);                    clearInterval(times);                    times=setInterval(function(){                        box_left+=10;                    box.style.left=box_left+‘px‘;                    if(box_left>=0){                        clearInterval(times);                    }                    },10)                }                box.onmouseout=function(){                    clearInterval(times)                    clearInterval(back_times);                    back_times=setInterval(function(){                        box_left-=10;                        box.style.left=box_left+‘px‘;                        if(box_left<=-250){                            clearInterval(back_times);                        }                    },10)                }            }    </script>