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Pig Latin Interpreter in javascript/node.js
Pig Latin interpreter
by Ben Buckman, July 20 2012
- All words beginning with a consonant have their first letter moved to the end of word followed by 'ay'.
Example: Hello -> Ellohay
- All words beginning with a vowel have their first letter moved to the end moved to the word followed by 'hay'.
Example: Another -> Notherahay
- All punctuation must be kept in place for example:
Bacon is awesome! Sometimes, in the morning, I'll have bacon on toast for breakfast.
Aconbay sihay wesomeahay! Ometimessay, nihay hetay orningmay, 'llihay avehay aconbay nohay oasttay orfay reakfastbay.
var pigLatin = module.exports = function(english) {
// make sure it's a string
english = '' + english;
// (only handle sentences. if paragraphs are expected, can extend this to split on non-space whitespace).
var splitWords = english.split(' '),
pigLatin = '',
splitWordsPigLatin = [];
// translate each word
// starts w/ a consonant or vowel?
// word can have an apostrophe in the middle. all other punctuation (comma etc) should be between words.
// quotation marks or other punctuation around the word are captured in first block.
// i flag indicates case-insensitive
var consonantStartPattern = /^[^a-z]*(([bcdfghjklmnpqrstvwxyz]){1}([a-z']*))/i,
consonantMatches = word.match(consonantStartPattern),
vowelStartPattern = /^[^a-z]*(([aeiou]){1}([a-z']*))/i,
vowelMatches = word.match(vowelStartPattern),
origWord, rebuiltWord = null;
// helper for both scenarios:
// want to keep case consistent: if 1st letter is uppercase now, make new 1st letter uppercase.
// (matches array is a reference)
var consistentCases = function(matches) {
if (/[A-Z]/.test(matches[2]) && matches[3].length > 0) {
// will be moved to the middle. is the rest of the word uppercase? (maybe it's an acronym)
if (matches[3] !== matches[3].toUpperCase()) matches[2] = matches[2].toLowerCase();
matches[3] = matches[3].replace(/^[a-z]{1}/, matches[3][0].toUpperCase());
if (consonantMatches !== null) {
for '"morning"' [w/quotes], matches will hold:
0: '"morning',
1: 'morning',
2: 'm',
3: 'orning',
4: index: 0,
5: input: '"morning",'
// console.log('consonsant matches:', consonantMatches);
origWord = consonantMatches[1];
rebuiltWord = '' + consonantMatches[3] + consonantMatches[2] + 'ay'; // morning => orningmay
else if (vowelMatches !== null) {
// console.log('vowel matches:', vowelMatches);
// [same match array structure as before]
origWord = vowelMatches[1];
rebuiltWord = '' + vowelMatches[3] + vowelMatches[2] + 'hay'; // Another => Notherahay
if (rebuiltWord) {
word = word.replace(origWord, rebuiltWord);
// (if original sentence had multiple spaces between words, this will return those spaces & preserve)
pigLatin = splitWordsPigLatin.join(' ');
return pigLatin;
// test helper
var assertTranslation = function(input, expectedOut) {
var assert = require('assert'),
actual = pigLatin(input);
console.log("Input:\t\t" + input);
console.log("Expected:\t" + expectedOut);
console.log("Actual:\t\t" + actual);
try {
assert.equal(actual, expectedOut);
return true;
catch(error) {
return false;
assertTranslation('Bacon is awesome! Sometimes, in the morning, I\'ll have bacon on toast for breakfast.',
'Aconbay sihay wesomeahay! Ometimessay, nihay hetay orningmay, \'llihay avehay aconbay nohay oasttay orfay reakfastbay.');
// test quotation marks around a word
assertTranslation('Sometimes, in the "morning", I eat bacon.',
'Ometimessay, nihay hetay "orningmay", Ihay atehay aconbay.');
// test extra whitespace
assertTranslation('Sometimes, in the morning',
'Ometimessay, nihay hetay orningmay');
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