My solution to the word frequency problem in JavaScript.

opt.js

const input = ["apple", "apple", "orange"];

const itemFreq = {};

for (const s of input) {
    if (!(s in itemFreq)) 
        itemFreq[s] = 0;
    itemFreq[s]++;
}

const filtered = input.sort((x, y) => { itemFreq[x] < itemFreq[y] ? 1 : itemFreq[x] > itemFreq[y] ? -1 : 0 })
                    .filter((x, i) => input.indexOf(x) === i);

for (const s of filtered) 
    console.log(`${s}: ${itemFreq[s]}`);