JSFiddle - React, Tailwind, and code Playground

JavaScript

function commaSeparateNumber(val){
    while (/(\d+)(\d{3})/.test(val.toString())){
      val = val.toString().replace(/(\d+)(\d{3})/, '$1'+','+'$2');
    }
    return val;
  }
var num = 10000;
console.log(commaSeparateNumber(parseFloat(num).toFixed(2)));