JSFiddle - React, Tailwind, and code Playground

by ianwong

HTML

<input id="input" type="text"></input>

<button id="button" type="button">Press</button>

<div id="output" type="text"></div>

JavaScript

var button = document.getElementById('button');
button.onclick = function() {
  var number = document.getElementById("input").value;
  
    if (isNaN(number)) {
        return '';
    }
    
    var asString = '' + Math.abs(number),
        numberOfUpToThreeCharSubstrings = Math.ceil(asString.length / 3),
        startingLength = asString.length % 3,
        substrings = [],
        isNegative = (number < 0),
        formattedNumber,
        i;
   
    if (startingLength > 0) {
        substrings.push(asString.substring(0, startingLength));
    }
    
    for (i=startingLength; i < asString.length; i += 3) {
        substrings.push(asString.substr(i, 3));
    }
    
    formattedNumber = substrings.join('.');
    if (isNegative) {
        formattedNumber = '-' + formattedNumber;
    }

    formattedNumber = formattedNumber +",00";
    
    document.getElementById("output").innerHTML = formattedNumber;
}