Shuffle iterator js module.

iterator-example.js

var slots = iterator([80, 60, 50, 40, 20, 10], { shuffle: true, pool: 2 });
var result = slots.next();

iterator.js

// --------------------------------------------------
// Iterator with shuffle support
// --------------------------------------------------
define(function (require) {
  
  // dependencies
  var _ = require('underscore');
  
  // default options
  var defaults = {
    repeat: true,
    shuffle: false,
    unique: true,
    pool: 1
  };
  
  // iterator module function
  function iterator(collection, options) {
    
    // validate params
    collection = _.toArray(collection);
    options = _.extend({}, defaults, options);
    if (options.pool < 1) options.pool = 1;
    if (collection.length < options.pool) {
      throw new Error('iterator: collection must be larger than pool.');
    }
    
    // expose instance methods
    var instance = {
      list: [],
      
      reset: function () {
        var rest = this.list.slice();
        this.list = rest.concat(collection);
        return this;
      },
      
      skip: function (item) {
        this.list = _.without(this.list, item);
        this.validate();
        return this;
      },
      
      validate: function () {
        if (options.repeat && this.list.length < options.pool) this.reset();
      },
      
      hasNext: function () {
        return this.list.length > 0;
      },
      
      next: function () {
        var result = this.list.shift();
        this.validate();
        return result;
      }
      
    };
    // override instance methods for shuffle
    options.shuffle && _.extend(instance, {
      
      reset: function () {
        var rest = this.list.slice();
        if (options.unique) {
          this.list = rest.concat(_.difference(_.shuffle(collection), rest));
        } else {
          this.list = rest.concat(_.shuffle(collection));
        }
        return this;
      }
      
    });
    // return instance with new list
    return instance.reset();
  }
  
  // return module (function)
  return iterator;
});