Dev.to Daily Challenge #80

80.js

// my JS engine doesn't have String.prototype.matchAll just yet
// so providing my own generator to do the same thing
function *matchAll(str, re) {
    let match;
    do {
        match = re.exec(str);       // get the first match of the regular expession
        if (match) yield match;     // if we have one, yield it
    } while (match != null);        // keep going until no more matches
}

const getLongestSequence = (str, re) =>
    Array.from(matchAll(str, re))   // generators are iterable
         .map(([seq]) => seq)       // extract the string from the regex match result
         .reduce((longest, cur) => 
             cur.length > longest.length ? cur : longest    // keep track of longest
         , "");

const getLongestVowelSequence = str => 
    getLongestSequence(str, /[aeiou]+/gi);  // use vowels -- g = global; i = case insensitive

const assert = (fn, expected) => {
    const result = fn();
    if (expected !== result) {
        throw new Error(`Expected ${expected}, saw ${result}`);
    }
    return result;
}

assert(() => getLongestVowelSequence("codewarriors"), "io");
assert(() => getLongestVowelSequence("aeiou"), "aeiou");
assert(() => getLongestVowelSequence("abebibobu"), "a");
assert(() => getLongestVowelSequence("vwlss"), "");
assert(() => getLongestVowelSequence(""), "");