unique token generation example

uniqueToken.js

// mock for collection.findOne
// the fourth call returns true the fifth returs false
var i = 0;
var isTokenInDB = function(token, callback) {
  setTimeout(function() {
    callback(null, (++i) < 5);
  }, 200);
};

// generate random string
var genToken = function() {
  return "" + Math.random();
};

// generate a unique token in the database
var genUniqueToken = function(cb) {
  var token = genToken();
  isTokenInDB(token, function(err, result) {
    if(result) {
      console.log('    ', token)
      genUniqueToken(cb);
    } else {
      cb(null, token);
    }
  });
};

// Usage
genUniqueToken(function(err, uniqueToken) {
  console.log('---> ' + uniqueToken);
});