Variable Type
(typeof foo)

Default function arguments
function scale(x, y)
  x = x || 1; // default to 1
  y = y || x; // default to x

Implicit delete
_ http://perfectionkills.com/understanding-delete/

Error Messaging, Error Types
try { throw new Error('foo') } catch (e) { /* e.message */ }
_ https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Error

Closures
_ http://jibbering.com/faq/notes/closures/

Prototypal Inheritance
_ http://javascript.crockford.com/prototypal.html
_ http://ejohn.org/apps/learn/#76
_ http://laktek.com/2011/02/02/understanding-prototypical-inheritance-in-javascript/

Object Enumeration (ECMA5)
_ http://javascriptweblog.wordpress.com/2011/02/28/javascript-object-keys-finally/

Threads
_ http://www.codeproject.com/Articles/37998/Simulate-Threading-Using-Javascript.aspx
_ http://ajaxian.com/archives/ajax-javascript-and-threads-the-finablel-truth

Browser History
_ https://developer.mozilla.org/en/DOM/Manipulating_the_browser_history#section_4

JS Sans-browser
_ http://ejohn.org/blog/bringing-the-browser-to-the-server/
_ https://github.com/thatcher/env-js
_ http://www.envjs.com/doc/guides#running-console
_ http://www.mozilla.org/rhino/shell.html

Cross site security
_ http://en.wikipedia.org/wiki/Cross-site_scripting
_ http://en.wikipedia.org/wiki/Cross-site_request_forgery

Not JS
_ https://github.com/jashkenas/coffee-script/wiki/List-of-languages-that-compile-to-JS

Textmate interactive console
_ http://www.metaskills.net/2010/7/9/interactive-javascript-console-with-textmate

TM JS tools bundle
_ https://github.com/johnmuhl/javascript-tools-tmbundle