partition an id of some sort into the unit interval, using md5 hexdigest

partitioner.js

var crypto = require('crypto');
var salt = "some_salt";

function place_in_interval(id) {
  var m = crypto.createHash('md5');
  m.update(salt + ":" + id)
  var key = m.digest('hex');
  return parseInt(key,16) / Math.pow(16,key.length);
}

place_in_interval(10);
place_in_interval("Asdf1234");