グローバルにあるArrayを汚さずにprototype拡張などを施したArrayを生成する

extArray.jsm

// Copyright (c) 2012 by teramako <teramako.at.gmail.com>
//
// This work is licensed for reuse under an MIT license. Details are
// given in the License.txt file included with this file.

const EXPORTED_SYMBOLS = [ "Array" ];

const bind = Function.prototype.bind,
      uncurryThis = bind.bind(bind.call),
      ArrayDescriptors = {
        isinstance: {
          value: function isinstance (obj) {
            return obj instanceof Array;
          },
        },
        toObject: {
          value: function toObject() {
            let obj = {};
            this.forEach(function ([k, v]) { obj[k] = v; });
            return obj;
          }
        },
        compact: {
          value: function compact () {
            return this.reduce(function(results, item) {
              item != null && results.push(item);
              return results;
            }, []);
          },
        },
        flatten: {
          value: function flatten () {
            return Array.prototype.concat.apply([], this);
          },
        },
        itervalues: {
          value: function itervalues () {
            for (let i = 0, len = this.length; i < len; ++i) {
              yield this[i];
            }
          }
        },
        iteritems: {
          value: function iteritems() {
            for (let i = 0, len = this.length; i < len; ++i) {
              yield [i, this[i]];
            }
          }
        },
        uniq: {
          value: function uniq () {
            return this.reduce(function(results, item) {
              results.indexOf(item) === -1 && results.push(item);
              return results;
            }, []);
          },
        },
      };


Object.defineProperties(Array.prototype, ArrayDescriptors);

var originalArray = Array;
Array = function Array (array) {
  return originalArray.slice(array);
};
Array.prototype = originalArray.prototype;

for (let [, key] in Iterator(Object.getOwnPropertyNames(originalArray))) {
  if (typeof originalArray[key] === "function") {
    Object.defineProperty(Array, key, Object.getOwnPropertyDescriptor(originalArray, key));
  }
}
for (let [key, desc] in Iterator(ArrayDescriptors)) {
  Object.defineProperty(Array, key, {
    value: uncurryThis(desc.value),
  });
}