ランダムな文字列の作成
const crypto = require("crypto");
const N = 18
let key = crypto.randomBytes(N).toString('base64').substring(0, N);
console.log(key);
const S="abcdefghijklmnopqrstuvwxyz0123456789=$%ABCDEFGHIJKLMNOPQRSTUVWXYZ"
let key2 = Array.from(crypto.randomFillSync(new Uint8Array(N))).map((n)=>S[n%S.length]).join('');
console.log(key2);