John Resig - ECMAScript 5 Strict Mode, JSON, and More
http://ejohn.org/blog/ecmascript-5-strict-mode-json-and-more/
John Resig - ECMAScript 5 Objects and Properties
http://ejohn.org/blog/ecmascript-5-objects-and-properties/

This new code gives you the ability to dramatically affect how users will be able to interact with your objects, allowing you to provide getters and setters, prevent enumeration, manipulation, or deletion, and even prevent the addition of new properties. In short: You will be able to replicate and expand upon the existing JavaScript-based APIs (such as the DOM) using nothing but JavaScript itself.

Ejacs is an Ecma-262 compliant JavaScript interpreter written entirely in Emacs Lisp. It should work in GNU Emacs versions 22 and higher.

Ejacs is an Ecma-262 compliant JavaScript interpreter written entirely in Emacs Lisp

JavaScript in emacs

ELispで書かれたEcma-262 インタプリタ。Emacs22以降で動くらしい

emacsでjsインタプリタ。alertとかDocument.writeとかが使えないから微妙