JSFiddle - React, Tailwind, and code Playground

by Yonatan Quintero

HTML

<input id="test" />

CSS

120000000

JavaScript

var input = document.getElementById('test');
input.style.textAlign = 'right';
input.onkeyup = function (e) {
    e.preventDefault();
    var keyCode = e.keyCode;
    if (keyCode !== 17 && keyCode !== 36 && keyCode !== 37 && keyCode !== 38 && keyCode !== 39 && keyCode !== 40) {
        var value = this.value;
        value = value.replace(/,/g, '');
        var characters = value.split('');
        var n = characters.length;
        var count = 0;
        var string = ',';
        if (n > 3) {
            for (var i = n; i > 0; i--) {
                if (count > 1 && count % 3 === 0) {
                    var start = 0;
                    var end = i;
                    var firtSubString = value.substr(start, end);
                    start = i;
                    end = n;
                    var lastSubString = value.substr(start, end);
                    value = firtSubString + string + lastSubString;
                }
                count++;
            }
        }
        this.value = value;
    }

}