added lengthGen.js

generators/lengthGen.js

@@ -0,0 +1,2 @@
+const { randomBytes } = require('crypto');
+module.exports = (length, charset) => [...randomBytes(length)].map((byte) => charset[Number(byte) % charset.length]).join('').slice(1).concat(charset[0]);

generators/zws.js

@@ -1,3 +1,3 @@
-const { randomBytes } = require('crypto');
+const lengthGen = require('./lengthGen');
 const zeroWidthChars = ['\u200B', '\u200C', '\u200D', '\u2060'];
-module.exports = ({ length }) => [...randomBytes(length)].map(byte => zeroWidthChars[Number(byte) % zeroWidthChars.length]).join('').slice(1) + zeroWidthChars[0];
+module.exports = ({ length }) => lengthGen(length, zeroWidthChars);