I have found a regex on stackoverflow to add a \',\' or \'.\' after every third number depending on your language.
(\\d)(?=(\\d\\d\\d)+(?!\\d))
You can try this:-
function thousandsSeparator(input) {
var output = input
if (parseFloat(input)) {
input = new String(input);
var parts = input.split(".");
parts[0] = parts[0].split("").reverse().join("").replace(/(\d{3})(?!$)/g, "$1,").split("").reverse().join("");
output = parts.join(".");
}
return output;
}