group-anagrams.js

function anagramNormalized(str) {
    return str.toLocaleLowerCase().split("").sort().join();
}

function isAnagram(a, b) {
    return anagramNormalized(a) === anagramNormalized(b);
}

function group(toBeGrouped, grouped = []) {
    if (!toBeGrouped.length) {
        return grouped;     
    } else {
        let nextGroup = toBeGrouped.filter(element => isAnagram(element, toBeGrouped[0]));
        let nextRest = toBeGrouped.filter(element => !isAnagram(element, toBeGrouped[0]));
        return group(nextRest, [...grouped, nextGroup]);
    }
}


const list = ['Tokyo', 'London', 'Rome', 'Donlon', 'Kyoto', 'Paris'];

console.log(group(list));