What is the best way to generate a 32 bit random unsigned number in Node? Here is what I tried:

var max32 = Math.pow(2, 32) - 1
var session = Math.floor(Math.random() * max32);

I need this for a unique id.

What is the best way to generate a 32 bit random unsigned number in Node? Here is what I tried:

var max32 = Math.pow(2, 32) - 1
var session = Math.floor(Math.random() * max32);

I need this for a unique id.

• javascript
• node.js

Share Improve this question Follow edited Jan 21, 2015 at 6:46 fvrghl asked Jan 21, 2015 at 6:39 fvrghlfvrghl 3,72866 gold badges3030 silver badges3737 bronze badges 3

• 1 The biggest 16 bit number is 65535, so if you're getting 100,000 you've got some real issues. – Pointy Commented Jan 21, 2015 at 6:42
• @Pointy transcribed it wrong. – fvrghl Commented Jan 21, 2015 at 6:46
• 1 I often use Math.random()*2**32|0 for int32 and Math.random()*2**32>>>0 for uint32. – bryc Commented May 22, 2022 at 10:54

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1 Answer 1

Sorted by: Reset to default 12

You could use crypto.randomBytes() like:

var crypto = require('crypto');
function randU32Sync() {
  return crypto.randomBytes(4).readUInt32BE(0, true);
}
// or
function randU32(cb) {
  return crypto.randomBytes(4, function(err, buf) {
    if (err) return cb(err);
    cb(null, buf.readUInt32BE(0, true));
  }
}