思路：1，临界值是 -150 和 0如果大于临界值，就要隐藏2，隐藏：速度为负显示：速度为正3,如果与临界值相等，就清空定时器否则，就运动

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html

<div id="div1"><span>分享到</span></div>

<style>#div1 { position:absolute; left:-150px; width:150px; height:200px; background:green;}#div1 span {position:absolute; right:-20px; top:70px; width:20px; height:60px; line-height:20px; background:blue;}</style>

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js

<script>window.onload = function(){	var oDiv = document.getElementById("div1");	var timer = null;		oDiv.onmouseover = function(){		showHide(0);	}		oDiv.onmouseout = function(){		showHide(-150);	}		//优化成一个方法	function showHide(iCritical){		clearInterval(timer);		var speed;		timer = setInterval(function(){			if(oDiv.offsetLeft > iCritical){				speed = -10;			}else{				speed = 10;			}						if(oDiv.offsetLeft == iCritical){				clearInterval(timer);			} else{				oDiv.style.left = oDiv.offsetLeft + speed + "px";			}					},30);	}			//展开	function show(){		clearInterval(timer);		timer = setInterval(function(){			if(oDiv.offsetLeft>=0){				clearInterval(timer);			}else{				oDiv.style.left = oDiv.offsetLeft + 10 + "px";			}		},30);	}		//隐藏	function hide(){		clearInterval(timer);		timer = setInterval(function(){			if(oDiv.offsetLeft==-150){	//这里是等于				clearInterval(timer);			}else{				oDiv.style.left = oDiv.offsetLeft - 10 + "px";			}		},30);	}	}</script>