prototype/src/enumerable.js

var $break = {};

var Enumerable = {
  each: function(iterator, context) {
    var index = 0;
    iterator = iterator.bind(context);
    try {
      this._each(function(value) {
        iterator(value, index++);
      });
    } catch (e) {
      if (e != $break) throw e;
    }
    return this;
  },
  
  eachSlice: function(number, iterator, context) {
    iterator = iterator ? iterator.bind(context) : Prototype.K;
    var index = -number, slices = [], array = this.toArray();
    while ((index += number) < array.length)
      slices.push(array.slice(index, index+number));
    return slices.collect(iterator, context);
  },

  all: function(iterator, context) {
    iterator = iterator ? iterator.bind(context) : Prototype.K;
    var result = true;
    this.each(function(value, index) {
      result = result && !!iterator(value, index);
      if (!result) throw $break;
    });
    return result;
  },

  any: function(iterator, context) {
    iterator = iterator ? iterator.bind(context) : Prototype.K;
    var result = false;
    this.each(function(value, index) {
      if (result = !!iterator(value, index))
        throw $break;
    });
    return result;
  },

  collect: function(iterator, context) {
    iterator = iterator ? iterator.bind(context) : Prototype.K;
    var results = [];
    this.each(function(value, index) {
      results.push(iterator(value, index));
    });
    return results;
  },
  
  detect: function(iterator, context) {
    iterator = iterator.bind(context);
    var result;
    this.each(function(value, index) {
      if (iterator(value, index)) {
        result = value;
        throw $break;
      }
    });
    return result;
  },
  
  findAll: function(iterator, context) {
    iterator = iterator.bind(context);
    var results = [];
    this.each(function(value, index) {
      if (iterator(value, index))
        results.push(value);
    });
    return results;
  },
  
  grep: function(pattern, iterator, context) {
    iterator = iterator ? iterator.bind(context) : Prototype.K;
    var results = [];
    this.each(function(value, index) {
      var stringValue = value.toString();
      if (stringValue.match(pattern))
        results.push(iterator(value, index));
    });
    return results;
  },
  
  include: function(object) {
    if (typeof this.indexOf == 'function')
      return this.indexOf(object) != -1;

    var found = false;
    this.each(function(value) {
      if (value === object) {
        found = true;
        throw $break;
      }
    });
    return found;
  },
  
  inGroupsOf: function(number, fillWith) {
    fillWith = fillWith === undefined ? null : fillWith;
    return this.eachSlice(number, function(slice) {
      while(slice.length < number) slice.push(fillWith);
      return slice;
    });
  },
  
  inject: function(memo, iterator, context) {
    iterator = iterator.bind(context);
    this.each(function(value, index) {
      memo = iterator(memo, value, index);
    });
    return memo;
  },
  
  invoke: function(method) {
    var args = $A(arguments).slice(1);
    return this.map(function(value) {
      return value[method].apply(value, args);
    });
  },
  
  max: function(iterator, context) {
    iterator = iterator ? iterator.bind(context) : Prototype.K;
    var result;
    this.each(function(value, index) {
      value = iterator(value, index);
      if (result == undefined || value >= result)
        result = value;
    });
    return result;
  },
  
  min: function(iterator, context) {
    iterator = iterator ? iterator.bind(context) : Prototype.K;
    var result;
    this.each(function(value, index) {
      value = iterator(value, index);
      if (result == undefined || value < result)
        result = value;
    });
    return result;
  },
  
  partition: function(iterator, context) {
    iterator = iterator ? iterator.bind(context) : Prototype.K;
    var trues = [], falses = [];
    this.each(function(value, index) {
      (iterator(value, index) ? 
        trues : falses).push(value);
    });
    return [trues, falses];
  },
  
  pluck: function(property) {
    var results = [];
    this.each(function(value) {
      results.push(value[property]);
    });
    return results;
  },
  
  reject: function(iterator, context) {
    iterator = iterator.bind(context);
    var results = [];
    this.each(function(value, index) {
      if (!iterator(value, index))
        results.push(value);
    });
    return results;
  },
  
  sortBy: function(iterator, context) {
    iterator = iterator.bind(context);
    return this.map(function(value, index) {
      return {value: value, criteria: iterator(value, index)};
    }).sort(function(left, right) {
      var a = left.criteria, b = right.criteria;
      return a < b ? -1 : a > b ? 1 : 0;
    }).pluck('value');
  },
  
  toArray: function() {
    return this.map();
  },
  
  zip: function() {
    var iterator = Prototype.K, args = $A(arguments);
    if (typeof args.last() == 'function')
      iterator = args.pop();

    var collections = [this].concat(args).map($A);
    return this.map(function(value, index) {
      return iterator(collections.pluck(index));
    });
  },
  
  size: function() {
    return this.toArray().length;
  },
  
  inspect: function() {
    return '#<Enumerable:' + this.toArray().inspect() + '>';
  }
}

Object.extend(Enumerable, {
  map:     Enumerable.collect,
  find:    Enumerable.detect,
  select:  Enumerable.findAll,
  filter:  Enumerable.findAll,
  member:  Enumerable.include,
  entries: Enumerable.toArray,
  every:   Enumerable.all,
  some:    Enumerable.any
});