Words Tracker

wordsTracker = (arr = []) => {
    return Object.entries(
        arr.reduce(
            (words, word) => (words[word] !== undefined ? Object.assign(words, { [word]: words[word] + 1 }) : words),
            arr
                .shift()
                .split(' ')
                .reduce((initial, word) => Object.assign(initial, { [word]: 0 }), {}),
        ),
    )
        .sort((a, b) => b[1] - a[1])
        .map(([word, count]) => `${word} - ${count}`)
        .join('\n');
};