Javascript showing in dollars

How would I display JavaScript output numbers in dollar format? I.E. $20.00 then $2,000.00 when the number gets larger. Ok so sample code.

if(this.getField("Account Name RequiredRow1").value !="") {
    event.value = 20;
}
else{
    event.value = "";
}

Answer

Here’s the function that I use.. Basically the same as @Senad’s except it adds commas:

function(val) {
    var valString = val.toFixed(2).toString().replace(/B(?=(?:d{3})+(?!d))/g, ",");
    return "$" + valString;
}