Javascript打字效果~

<script language="Javascript">
var msg = "看看打字效果如何，不知道用PHP怎么做，这个是用JAVASCRIPT做的。！！！！" ;
var interval = 120
var spacelen = 120;
var space10=" ";
var seq=0;
function Helpor_net() {
len = msg.length;
window.status = msg.substring(0, seq+1);
seq++;
if ( seq >= len ) {
seq = 0;
window.status = '';
window.setTimeout("Helpor_net();", interval );
}
else
window.setTimeout("Helpor_net();", interval );
}
Helpor_net();
</script>