Generate a unique ID string in Node.js?

If you don't mind using a NPM package, nanoid is a great tool.

Install it like this:

npm install --save nanoid

And it can be put to use like this:

const nanoid = require("nanoid")

const generateUniqueId = function(length) {
  const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

  const generator = nanoid.customAlphabet(alphabet, length)

  return generator()
}

This function takes a given length and returns a random ID string with that given length. The alphabet contains the numbers and letters to include in the ID. Change that to whatever you want in yours.

You'd use the function like this:

generateUniqueId(12) // returns "pvSCCiqx0WsD"

You can test the probability of creating duplicate IDs here: https://zelark.github.io/nano-id-cc/.

function guidGenerator() {
    var S4 = function() {
       return (((1 + Math.random()) * 0x10000) | 0).toString(16).substring(1)
    }

    return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4())
}

This function returns a UUID in a 5f924b45-06ba-0e65-7407-853005e2d539 format.