Working with Dollars & Cents in JavaScript: The Definitive Guide

dollars_and_cents.js

console.log("****************************************************");
console.log("**** Working With Dollars & Cents in JavaScript ****");
console.log("****          ~ The Definitive Guide ~          ****");
console.log("****************************************************");
console.log('\n');

const formatAsDollarsAndCents = (value) => {

    var newValue = parseFloat(value);

    newValue = newValue.toFixed(2);

    return newValue;
}

// Floating Point Numbers Formatted to 2 Decimal Places
console.log("Floating Point Numbers Formatted to 2 Decimal Places");

const nonStandardAmountFormatted = formatAsDollarsAndCents(34.089999999999996);
console.log(nonStandardAmountFormatted);

const oneDecimalPlaceFormatted = formatAsDollarsAndCents(1.1);
console.log(oneDecimalPlaceFormatted);

const wholeNumberFormatted = formatAsDollarsAndCents(1);
console.log(wholeNumberFormatted);

console.log('\n');


// Strings Formatted to 2 Decimal Places
console.log("Cast As String...");

const nonStandardAmountFormattedAsString = nonStandardAmountFormatted.toString();
console.log('$' + nonStandardAmountFormattedAsString);

const oneDecimalPlaceFormattedAsString = oneDecimalPlaceFormatted.toString();
console.log('$' + oneDecimalPlaceFormattedAsString);

const wholeNumberFormattedAsString = wholeNumberFormatted.toString();
console.log('$' + wholeNumberFormattedAsString);

console.log('\n');

// Need to add commas? Here's the regex magic sprinkled in...
const myNumber = 1300000.89
const myNumberAsString = myNumber.toString();
const myNumberWithCommas = myNumberAsString.replace(/\d(?=(\d{3})+\.)/g, '$&,');
console.log('Add commas... ');
console.log('$' + myNumberWithCommas);

// Edge case, need to add commas to a whole number? I've written a function that 
// will add commas to a string of numeric characters. This is helpful when working
// with integers, as the regular expression above does not work with whole numbers.
// (One could write a regular expression that works with whole numbers, but I'm not 
// very good with regex so I just wrote a function and moved on with my life ;)
function getWholeNumberWithCommas(wholeNumberStr) {
  
  // Step One, Reverse String
  var reversedString = "";
  var indexOfLastChar = wholeNumberStr.length - 1;
  for (var i = indexOfLastChar; i >= 0; i--) {
    reversedString = reversedString + wholeNumberStr[i];
  }

  // Step Two, Add Commas Every Third Char
  var reversedStringWithCommas = "";
  for (var i = 0; i < reversedString.length; i++) {
    // every third char, add a comma and the next char
    if (i % 3 === 0 && i !== 0) {
      reversedStringWithCommas = reversedStringWithCommas + "," + reversedString[i];
    } else {
      reversedStringWithCommas = reversedStringWithCommas + reversedString[i];
    }
  }

  // Step Three, Reverse reversedStringWithCommas, and we'll have 
  // the whole number with commas that we want
  var wholeNumberWithCommas = "";
  indexOfLastChar = reversedStringWithCommas.length - 1;
  for (var i = indexOfLastChar; i >= 0; i--) {
    wholeNumberWithCommas = wholeNumberWithCommas + reversedStringWithCommas[i];
  }

  // Step Four, return wholeNumberWithCommas
  return wholeNumberWithCommas;
}

console.log('\n');

var testNumber = "9283749823749872398472938742983748";
var testNumberWithCommas = getWholeNumberWithCommas(testNumber);
console.log('Add commas to a whole number (represented as a string)');
console.log(testNumberWithCommas);

console.log('\n');
console.log("****************************************************");
console.log("****************************************************");
console.log("****************************************************");