A Pen by Chris Hicks.

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<p>Given any integer print an English phrase that describes the integer. (e.g. "One Thousand, Three Hundred Twenty Four").</p>

<div id="log"></div>

integer-to-english.markdown

integer to english

Given any integer print an English phrase that describes the integer. (e.g. "One Thousand, Three Hundred Twenty Four").

A Pen by Chris Hicks on CodePen.

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script.js

function log(text) {
  $('#log').append(text + "<br>\n");
}

function int2Eng(num) {
  'use strict';
  
  var 
    ones = ["Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine"],
    teens = ["Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"],
    tens = ["", "", "Twenty", "Thirty", "Fourty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"],
    numberGroups = ["", "Thousand", "Million", "Billion"],
  
    /* Convert 12300 to 300,12 so we can work with the order of magnitudes easier.
     * This makes 300 the first coma separated group, so we know not to append a 
     * number group like 'Thousand' or 'Million'. 12 is the second group, so we 
     * know it will be in the 'Thousand' range and we can append that to the 
     * phrase 'Twelve' to get 'Tweleve Thousand'
     */
    reversed = reverseStr(num.toString()),  
    groups = reversed.match(/\d{1,3}/g),group,
    output = [];
  
  // Blow up if not a number
  // Blow up if negative
  // Blow up if greater than 999,999,999,999
  
  log(" ");
  log('num: ' + num);
  
  // Use groups length to count down the order of magnitude.
  // Print number for 12, group 1 -> Tweleve Thousand
  // Print number for 300, group 0 -> Three Hundred
  for(group = groups.length - 1; group >= 0; group--) {
   output.push(printNumber(reverseStr(groups[group]), group));
  }
  
  // join the two phrases together...
  log(output.join(', '));
  
  function printNumber (number, numberGroup) {
    var length = number.length, 
        output = [];
    
    if (length === 1) {
      output.push(singleDigit(number));  
    }
    
    if (length === 2) {
      output.push(doubleDigit(number));
    }
    
    if (length === 3) {
      output.push(tripleDigit(number));
    }
    
    output.push(numberGroups[numberGroup])
    return output.join(' ');
  }
  
  function singleDigit(number) {
    return ones[number.charAt(0)];
  }
  
  function doubleDigit(number) {
    var output = [];
    if (number == "00") { // We don't say Zero Zero or Five Hundred Zero
      return '';
    } else if (number.charAt(0) === '1') { // Cover the things between 9 and 20
      output.push(teens[number.charAt(1)]);  
    } else { // Everything else is easy.
      output.push(tens[number.charAt(0)]);
      output.push(ones[number.charAt(1)]);
    }
    return output.join(' ');
  }
  
  function tripleDigit(number) {
    var output = [];
    output.push(singleDigit(number.substring(0,1)));
    output.push("Hundred");
    output.push(doubleDigit(number.substring(1,3)));
    return output.join(' ');
  }
  
  function reverseStr(str) {
    return str.split('').reverse().join(''); 
  }
}

int2Eng(1); // One
int2Eng(10); // Ten
int2Eng(12); // Twelve
int2Eng(21); // Twenty One
int2Eng(123); // One Hundred Twenty Three 
int2Eng(300); // Three Hundred
int2Eng(301); // Three Hundred One
int2Eng(1234); // One Thousand, Two Hundred Thirty Four 
int2Eng(12345); // Twelve Thousand, Three Hundred Fourty Five
int2Eng(12312); // Twelve Thousand, Three Hundred Twelve
int2Eng(123456); // One Hundred Twenty Three Thousand, Four Hundred Fifty Six
int2Eng(3744892348); // Three Billion, Seven Hundred Fourty Four Million, Eight Hundred Ninety Two Thousand, Three Hundred Fourty Eight