4kyu-mostFrequentlyUsedWords.js

'use strict';

// Source: https://www.codewars.com/kata/51e056fe544cf36c410000fb

// DESCRIPTION:

// Write a function that, given a string of text (possibly with punctuation and 
// line-breaks), returns an array of the top-3 most occurring words, in 
// descending order of the number of occurrences.

// Assumptions:

// - A word is a string of letters (A to Z) optionally containing one or more 
// apostrophes (') in ASCII. (No need to handle fancy punctuation.)
// - Matches should be case-insensitive, and the words in the result should be 
// lowercased.
// - Ties may be broken arbitrarily.
// - If a text contains fewer than three unique words, then either the top-2 or 
// top-1 words should be returned, or an empty array if a text contains no words.

// Examples:

// top_3_words("In a village of La Mancha, the name of which I have no desire to 
// call to mind, there lived not long since one of those gentlemen that keep a 
// lance in the lance-rack, an old buckler, a lean hack, and a greyhound for 
// coursing. An olla of rather more beef than mutton, a salad on most nights, 
// scraps on Saturdays, lentils on Fridays, and a pigeon or so extra on Sundays, 
// made away with three-quarters of his income.")
// # => ["a", "of", "on"]

// top_3_words("e e e e DDD ddd DdD: ddd ddd aa aA Aa, bb cc cC e e e")
// # => ["e", "ddd", "aa"]

// top_3_words("  //wont won't won't")
// # => ["won't", "wont"]


function topThreeWords(text) {
    let allWordsArray = text.toLowerCase().match(/[a-z]+'?[a-z]*/g);
    if (!allWordsArray) return [];

    let uniqueWordsObj = {};
    for (let word of allWordsArray) {
        if (uniqueWordsObj[word]) uniqueWordsObj[word]++;
        else uniqueWordsObj[word] = 1;
    }

    let uniqueWordsArray = Object.keys(uniqueWordsObj).sort((a, b) => {
        return uniqueWordsObj[b] - uniqueWordsObj[a]
    });

    return uniqueWordsArray.slice(0, 3);
}