hokaccha https://blog.hatena.ne.jp/hokaccha/ hokaccha memo https://hokaccha.hatenablog.com/ JavaScript Array.prototype.keysはIteratorを返すのでArray.fromに食わせる Array.from(Array(5).keys()); //=> [0, 1, 2, 3, 4] もしくは Array.from({ length: 5 }).map((v, k) => k); //=> [0, 1, 2, 3, 4] Array.fromの第二引数はmap的な役割があるので Array.from({ length: 5 }, (v, k) => k); //=> [0, 1, 2, 3, 4] こんな感じ。 [追記] 便利。 ES6でN個の配列 - hokaccha ham… 190 <iframe src="https://hatenablog-parts.com/embed?url=https%3A%2F%2Fhokaccha.hatenablog.com%2Fentry%2F2016%2F03%2F21%2F162936" title="ES6でN個の配列 - hokaccha memo" class="embed-card embed-blogcard" scrolling="no" frameborder="0" style="display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;"></iframe> Hatena Blog https://hatena.blog 2016-03-21 16:29:36 rich https://hokaccha.hatenablog.com/entry/2016/03/21/162936 1.0 100%