JSFiddle - React, Tailwind, and code Playground

JavaScript

function addPunctuation(number){
    var array = number.toString().split("");
    var output = "";
    var first = true;
    for(var i = array.length-1; i >= 0; i--){
    	if((array.length-i-1) % 3 === 0){
        if(first){
          first = false;
        }else{
          output = "," + output;
        }      
      }
      output = array[i] + output;
    }
    return output;
}

alert(addPunctuation(12313232231));