js中控制物体无延迟移动的思路

自由自动：

window.onload=function(){var box=document.getElementById("box");//初始化状态var left=false;var top=false;var right=false;var down=false;//状态1document.onkeydown=function(ev){var e=ev||event;var code=e.keyCode;document.title=code;switch(code){case 37:left=true;break;case 38:top=true;break;case 39:right=true;break;case 40:down=true;break;}}//状态2document.onkeyup=function(ev){var e=ev||event;var code=e.keyCode;switch(code){case 37:left=false;break;case 38:top=false;break;case 39:right=false;break;case 40:down=false;break;}}var timer=setInterval(function(){if(left){box.style.left=box.offsetLeft-10+'px';}if(top){box.style.top=box.offsetTop-10+'px';}if(right){box.style.left=box.offsetLeft+10+'px';}if(down){box.style.top=box.offsetTop+10+'px';}},50)}