Check if two strings are anagrams

anagrams.js

function anagrams(s1, s2) {
    if (s1.length !== s2.length)
        return false

    let fc1 = frequencyCounter(s1)
    let fc2 = frequencyCounter(s2)

    for (let key in fc1)
        if (!key in fc2 || fc1[key] !== fc2[key])
            return false

    return true
}