prototype/src/array.js

function $A(iterable) {
  if (!iterable) return [];
  if (iterable.toArray) return iterable.toArray();
  var length = iterable.length, results = new Array(length);
  while (length--) results[length] = iterable[length];
  return results;
}

if (Prototype.Browser.WebKit) {
  function $A(iterable) {
    if (!iterable) return [];
    if (!(Object.isFunction(iterable) && iterable == '[object NodeList]') &&
        iterable.toArray) return iterable.toArray();
    var length = iterable.length, results = new Array(length);
    while (length--) results[length] = iterable[length];
    return results;
  }
}

Array.from = $A;

Object.extend(Array.prototype, Enumerable);

if (!Array.prototype._reverse) Array.prototype._reverse = Array.prototype.reverse;

Object.extend(Array.prototype, {
  _each: function(iterator) {
    for (var i = 0, length = this.length; i < length; i++)
      iterator(this[i]);
  },
  
  clear: function() {
    this.length = 0;
    return this;
  },
  
  first: function() {
    return this[0];
  },
  
  last: function() {
    return this[this.length - 1];
  },
  
  compact: function() {
    return this.select(function(value) {
      return value != null;
    });
  },
  
  flatten: function() {
    return this.inject([], function(array, value) {
      return array.concat(Object.isArray(value) ?
        value.flatten() : [value]);
    });
  },
  
  without: function() {
    var values = $A(arguments);
    return this.select(function(value) {
      return !values.include(value);
    });
  },
  
  reverse: function(inline) {
    return (inline !== false ? this : this.toArray())._reverse();
  },
  
  reduce: function() {
    return this.length > 1 ? this : this[0];
  },
  
  uniq: function(sorted) {
    return this.inject([], function(array, value, index) {
      if (0 == index || (sorted ? array.last() != value : !array.include(value)))
        array.push(value);
      return array;
    });
  },
  
  intersect: function(array) { 
    return this.uniq().findAll(function(item) { 
      return array.detect(function(value) { return item === value });
    }); 
  },
  
  clone: function() {
    return [].concat(this);
  },
  
  size: function() {
    return this.length;
  },
  
  inspect: function() {
    return '[' + this.map(Object.inspect).join(', ') + ']';
  },
  
  toJSON: function() {
    var results = [];
    this.each(function(object) {
      var value = Object.toJSON(object);
      if (!Object.isUndefined(value)) results.push(value);
    });
    return '[' + results.join(', ') + ']';
  }
});

// use native browser JS 1.6 implementation if available
if (Object.isFunction(Array.prototype.forEach))
  Array.prototype._each = Array.prototype.forEach;

if (!Array.prototype.indexOf) Array.prototype.indexOf = function(item, i) {
  i || (i = 0);
  var length = this.length;
  if (i < 0) i = length + i;
  for (; i < length; i++)
    if (this[i] === item) return i;
  return -1;
};

if (!Array.prototype.lastIndexOf) Array.prototype.lastIndexOf = function(item, i) {
  i = isNaN(i) ? this.length : (i < 0 ? this.length + i : i) + 1;
  var n = this.slice(0, i).reverse().indexOf(item);
  return (n < 0) ? n : i - n - 1;
};

Array.prototype.toArray = Array.prototype.clone;

function $w(string) {
  if (!Object.isString(string)) return [];
  string = string.strip();
  return string ? string.split(/\s+/) : [];
}

if (Prototype.Browser.Opera){
  Array.prototype.concat = function() {
    var array = [];
    for (var i = 0, length = this.length; i < length; i++) array.push(this[i]);
    for (var i = 0, length = arguments.length; i < length; i++) {
      if (Object.isArray(arguments[i])) {
        for (var j = 0, arrayLength = arguments[i].length; j < arrayLength; j++) 
          array.push(arguments[i][j]);
      } else { 
        array.push(arguments[i]);
      }
    }
    return array;
  };
}