Object.create(null)

TypeError: Cannot convert object to primitive value

ECMAScript 6th の仕様書を読み始めた

Standard ECMA-262

ちゃんと読んだことなかったし, 電車移動中に暇だったのでとりあえず第 4 節まで読んだ (歴史とか用語定義とか).

おまけ

4.3.17 String value

primitive value that is a finite ordered sequence of zero or more 16-bit unsigned integer

NOTE A Sing value is a member of the String type. Each integer value in the sequence usually represents a single 16-bit unit of UTF-16 text. However, ECMAScript does not place any restrictions or requirements on the values except that they must be 16-bit unsigned integers.

(PDF 版より引用, 強調筆者)

急に歌うよ.