Group duplicate prefixes in the strings: (src: string[]) => string[]

groupByPrefix.js

const getInitials = (src, length) => {
    if (length === void 0) { length = 1; }
    return Array.from(new Set(src.map(v => v.substring(0, length))));
};
export default src => getInitials(src).map(initial => {
    const list = src.filter(v => v.match(`^${initial}`));
    const rec = (prev, length) => {
        if (length === void 0) { length = 2; }
        const _a = getInitials(list, length);
        const word = _a[0];
        const l = _a.slice(1).length;
        return l || list[0].length < length ? prev : rec(word, length + 1);
    };
    return rec(initial);
});