A "unique collection" object. Implemented as a node.js module.

tests.js

var UniqueCollection = require('./UniqueCollection');

var testCollection = new UniqueCollection();
console.log('Create new collection');
console.log('Collection contents   :', testCollection.list(), "\n");

var testItem = testCollection.add();
console.log('Add new item          :', testItem);
console.log('Collection contents   :', testCollection.list(), "\n");

console.log('Contains item '+testItem+' :', testCollection.contains(testItem));
console.log('Collection contents   :', testCollection.list(), "\n");

console.log('Contains item FAKE    :', testCollection.contains('FAKE'));
console.log('Collection contents   :', testCollection.list(), "\n");

console.log('Remove item '+testItem+'   :', testCollection.remove(testItem));
console.log('Collection contents   :', testCollection.list(), "\n");

console.log('Remove item FAKE      :', testCollection.remove('FAKE'));
console.log('Collection contents   :', testCollection.list(), "\n");

UniqueCollection.js

/**
 * A Unique Collection Object
 *   Items are alphanumeric strings (defined by createItem function)
 *   Items are 7 characters long (defined by itemLength variable)
 */
function UniqueCollection() {
  var items      = [];
  var itemLength = 7;

  /* Create a new item */
  var createItem = function() {
    var item  = '';
    var chars = 'abcdefghijklmnopqrstuvwxyz0123456789';

    for (var i=0; i<itemLength; i++) {
      item += chars.charAt(Math.floor(Math.random() * chars.length));
    };
    return item;
  };

  /* Add a new item to the collection */
  this.add = function() {
    var item = createItem();

    while (items.indexOf(item) !== -1) {
      item = createItem();
    }
    items.push(item);
    return item
  };

  /* Remove a specified item from the collection */
  this.remove = function(item) {
    var i = items.indexOf(item);

    if (i === -1) {
      return false;
    } else {
      items.splice(i, 1);
      return true;
    }
  };

  /* Check if a specified item is in the collection */
  this.contains = function(item) {
    var i = items.indexOf(item);
    return (i === -1) ? false : true;
  };

  /* Return an array of all items in collection */
  this.list = function() {
    return items.slice();
  };
}

module.exports = UniqueCollection;