Discussion on: The moment I realized forEach() does not return anything.

[Kay N.]

Yes that sure does the job <3! Thanks for recommending!

[Thomas Broyer]

And you may want to use new Set(array1) instead of your hashTable.

const haveCommonItems = (array1, array2) => {
    const array1set = new Set(array1)
    return array2.some(array1set.has)
}

(disclaimer: untested code snippet)

[Kay N.]

Awesome! Here's my tested code:

const haveCommonItems = (array1, array2) => {
    const array1set = new Set(array1);
    return array2.some(item => array1set.has(item));

haveCommonItems(animals, pets); // returns "true"
}

Very clean and time optimized! Thanks again everyone!