<div id="here"></div>
<script>
function sett(){
document.getElementById('here').innerHTML+='a';
}
setInterval("sett();",500);
</script>
<script>
function sett(){
document.getElementById('here').innerHTML+='a';
}
setInterval("sett();",500);
</script>
<script>
function sett(){
var v=document.getElementById('here');
if(v.innerHTML.length>=5)return;
v.innerHTML+='a';
}
setInterval("sett();",500);
</script>