[JavaScript] Object.definePropertyのラッパー ref: http://qiita.com/MizuiroFolder/items/a001977cdb267d65ef6b

constant

function constant(key, value){
  defProp(window, key, value, 1);
  return value;
}

constant('FOO_BAR', 'foo bar') //=> 'foo bar'
FOO_BAR //=> 'foo bar'
FOO_BAR = 'baz' //=> 'baz'
FOO_BAR //=> 'foo bar'
(function(){ 'use strict'; FOO_BAR = 'baz' })() //~> TypeError: "FOO_BAR" is read-only
FOO_BAR //=> 'foo bar'

defProp

function defProp(targets, key, value, descriptorMask){
  if(typeof descriptorMask === 'undefined') descriptorMask = 7
  Object.defineProperty(targets, key, {
    value:        value,
    enumerable:   descriptorMask & 1, // 列挙可能か
    configurable: descriptorMask & 2, // 削除可能か
    writable:     descriptorMask & 4, // 変更可能か
  });
  return targets;
}

file1.js

defProp(Object.prototype, 'keys', function(){
  return Object.keys(this);
}, 6); //=> Object.prototype

({ foo: 9, bar: 8 }).keys() //=> ['foo','bar']