js中settimeout方法加参数

<script type="text/javascript"> 
function timedMsg() 
{ 
var a ="dd"; 
var t=setTimeout(function(){ cao(a);},3000) 
} 
function cao(a) 
{ 
alert(a); 
} 
</script> 
</head> 
<input type="button" value="显示定时的警告框" onClick = "timedMsg()">

/* for (var i=0;i<points.length;i++){ 
AddGuiJi(points[i],value); 
//var t=setTimeout(function(){ AddGuiJi(points[i],value);},2000*i) 
} */

var timerr; 
function xunhuanlian(points,value){ 
if(replayi<points.length){ 
AddGuiJi(points[replayi],value); 
replayi++; 
timerr=setTimeout(function(){ xunhuanlian(points,value);},1000); 
} 
else{ 
replayi =0; 
clearTimeout(timerr); 
} 
/* for (var i=0;i<points.length;i++){ 
AddGuiJi(points[i],value); 
//var t=setTimeout(function(){ AddGuiJi(points[i],value);},2000*i) 
} */ 
}