const price = 15000
const price_comma = price.toString().replace(/\B(?<!\.\d*)(?=(\d{3})+(?!\d))/g, ",")
document.writeln(price_comma)

document.writeln("<br>")

const num = 9542.1234
const num_commpa = num.toString().replace(/\B(?<!\.\d*)(?=(\d{3})+(?!\d))/g, ",")
document.writeln(num_commpa)