Javascript FormatNumber function implementation method

Since this function is not available in JavaScript, how should we implement it? I will give this function below. You can add this sentence to your html page, or you can use it
<!-- #include file="" --> Add to your asp page; or use
<? include("") ?> Add to php page; or use
<%@ #include file="" %>Add to jsp page.
This formatnumber subfunction is as follows:
<script language=javascript>
<!--
function formatnumber(srcstr,nafterdot){
var srcstr,nafterdot;
var resultstr,nten;
srcstr = ""+srcstr+"";
strlen = ;
dotpos = (".",0);
if (dotpos == -1){
resultstr = srcstr+".";
for (i=0;i<nafterdot;i++){
resultstr = resultstr+"0";
}
return resultstr;
}
else{
if ((strlen - dotpos - 1) >= nafterdot){
nafter = dotpos + nafterdot + 1;
nten =1;
for(j=0;j<nafterdot;j++){
nten = nten*10;
}
resultstr = (parsefloat(srcstr)*nten)/nten;
return resultstr;
}
else{
resultstr = srcstr;
for (i=0;i<(nafterdot - strlen + dotpos + 1);i++){
resultstr = resultstr+"0";
}
return resultstr;
}
}
}