var obj = new Object({'name': 'hoge'}); console.log(obj); // =>Object {name: "hoge"} Object.prototype.test = 'test!'; console.log(obj); // =>Object {name: "hoge", test: "test!"} /* ECMAScript 3 */ console.log(obj.constructor.prototype); // =>Object {test: "test!"} /* ECMAScript 5 */ console.log(Object.getPrototypeOf(obj)); // =>Object {test: "test!"}