Permutron

A while back I needed a way to generate unique ids on the client-side using JavaScript. I wrote Permutron to provide a simple utility to allow me to have as many ids as necessary. Permutron simply returns the next id in a sequence that you configure. It does not have any knowledge of what you are applying the ids to, and it will not be persistent between browser sessions. (In my use case, I needed ids that were unique for the life of the user's session.)

How to use it

• First, include the Permutron.js file in your page.
• "New" up a Permutron object.
• Permutron takes 3 arguments, only the first one is required
  • maxIdLength - the max number of characters you want the id to reach.
  • isFixed - if you always want your id to be the length you specified as maxIdLength, this should be true. If set to false, the ids will start as 1 character and work up to your maxIdLength. It defaults to false.
  • charset - the list of characters you want to use as the pool of characters for the generator. It defaults to [a-zA-Z].
• As you need ids, call "next()"
• You can also access the total ids possible with the configuration you provided by calling "maxIdsPossible()"
• Your Permutron object will set "depletedAvailableIds" to true when it has exhausted the possible permutations.

JavaScript

// Set up a Permutron, up to 5 character length Ids, variable width:
var defaultPermutron = new Permutron(5);

// How many can this guy generate?
var totalIdsPossible = defaultPermutron.maxIdsPossible();

// when you need a new id
var id = defaultPermutron.next();

// But what if I want to use only "ABCDE" as the character set
// *and* I want my ids to always be 7 chars long?
var otherPermutron = new Permutron(7, true, "ABCDE");