键值控制

键值监听
<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>onkeydown</title>
</head>
<body>
	<div id="div" style="100px;height: 100px;background: blue;position:absolute;top:0;left:0;"></div>
</body>
<script type="text/javascript">
	var oDiv = document.getElementById('div');
	var timer = null ;
	var iCode = {}; 
	document.onkeydown = function(ev){
        var ev = ev || window.event ;
        iCode[ev.keyCode]= true;//获取键值。
        console.log(iCode);//利用JSON存储
    }
	document.onkeyup = function(ev){
        var ev = ev || window.event ;
        iCode[ev.keyCode] = false ;
	}
	timer = setInterval(function(){
       if(iCode[37]){//左键
        	oDiv.style.left = oDiv.offsetLeft - 10 + 'px'; 
       }if(iCode[38]){ //上键
        	oDiv.style.top = oDiv.offsetTop - 10 + 'px';
       }if(iCode[39]){//右键
        	oDiv.style.left = oDiv.offsetLeft + 10 + 'px'; 
       }if(iCode[40]){ //下键
        	oDiv.style.top = oDiv.offsetTop+ 10 + 'px'; 
	   }
	},20);
</script>
</html>