Pig Latin Interpreter in javascript/node.js

pig-latin.js

/*
Pig Latin interpreter
by Ben Buckman, July 20 2012

Rules:
- 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
  splitWords.forEach(function(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);
      
      consistentCases(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]
      
      consistentCases(vowelMatches);

      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)
    splitWordsPigLatin.push(word);
  });  
  
  
  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);
    console.log("Correct!\n");
    return true;
  }
  catch(error) {
    console.error("Incorrect!\n");
    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');