这里可实现点击向右，方块向右移动，点击向左，方块向左移动的效果
可以用setInterval来实现过多长时间，div移动多长的距离来实现运动效果。
要点一：如果元素的左边距离小于目标距离，则是正向移动，否则是负向移动
if(run.offsetLeft <target){ speed = 2; }else{ speed = -2; }
要点二：如果元素的左边距离等于目标距离，停止定时器，否则，元素的左边距离等于现在的左边距离加上速度值。
if(run.offsetLeft ==target){ clearInterval(timer); } else{ run.style.left = run.offsetLeft +speed +"px"; }
上代码
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>无标题文档</title> <style> body{margin:0; padding:0;} #run{width:100px; height:100px; background:#06c; position:absolute; border:1px solid #000; left:0;} </style> <script> window.onload = function(){ var run = document.getElementById("run"); var btn = document.getElementById("btn"); var btn1 = document.getElementById("btn1"); var speed = 2; var timer = null; btn.onclick = function(){ startrun(300); } btn1.onclick = function(){ startrun(0); } function startrun(target){ clearInterval(timer); timer = setInterval(function(){ if(run.offsetLeft <target){ speed = 2; }else{ speed = -2; } if(run.offsetLeft ==target){ clearInterval(timer); } else{ run.style.left = run.offsetLeft +speed +"px"; } },30) } } </script> </head> <body> <input type="button" value="运动向右"> <input type="button" value="运动向左"> <div></div> </body> </html>