join・splitの使い方 joinの使い方 >main.js { const a = [2022, 12, 25]; console.log(a.join('/')); console.log(a.join('')); } 結果 >2022/12/25 >20221225 splitの使い方 { const b = '20:23:55' console.log(b.split(':')); } 結果 > ['20', '23', '55…