Secure random token in Node.js

Try crypto.randomBytes():

require('crypto').randomBytes(48, function(err, buffer) {  var token = buffer.toString('hex');});

The 'hex' encoding works in node v0.6.x or newer.

Synchronous option in-case if you are not a JS expert like me. Had to spend some time on how to access the inline function variable

var token = crypto.randomBytes(64).toString('hex');

1. Using nanoid third party library [NEW!]

A tiny, secure, URL-friendly, unique string ID generator for JavaScript

https://github.com/ai/nanoid

import { nanoid } from "nanoid";const id = nanoid(48);

2. Base 64 Encoding with URL and Filename Safe Alphabet

Page 7 of RCF 4648 describes how to encode in base 64 with URL safety.You can use an existing library like base64url to do the job.

The function will be:

var crypto = require('crypto');var base64url = require('base64url');/** Sync */function randomStringAsBase64Url(size) {  return base64url(crypto.randomBytes(size));}

Usage example:

randomStringAsBase64Url(20);// Returns 'AXSGpLVjne_f7w5Xg-fWdoBwbfs' which is 27 characters length.

Note that the returned string length will not match with the size argument (size != final length).

3. Crypto random values from limited set of characters

Beware that with this solution the generated random string is not uniformly distributed.

You can also build a strong random string from a limited set of characters like that:

var crypto = require('crypto');/** Sync */function randomString(length, chars) {  if (!chars) {    throw new Error('Argument \'chars\' is undefined');  }  const charsLength = chars.length;  if (charsLength > 256) {    throw new Error('Argument \'chars\' should not have more than 256 characters'      + ', otherwise unpredictability will be broken');  }  const randomBytes = crypto.randomBytes(length);  let result = new Array(length);  let cursor = 0;  for (let i = 0; i < length; i++) {    cursor += randomBytes[i];    result[i] = chars[cursor % charsLength];  }  return result.join('');}/** Sync */function randomAsciiString(length) {  return randomString(length,    'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789');}

Usage example:

randomAsciiString(20);// Returns 'rmRptK5niTSey7NlDk5y' which is 20 characters length.randomString(20, 'ABCDEFG');// Returns 'CCBAAGDGBBEGBDBECDCE' which is 20 characters length.