The history of “typeof null”

Update 2013-11-05: I take a look at the C code of typeof to better explain why typeof null results in 'object'.

In JavaScript, typeof null is 'object', which incorrectly suggests that null is an object (it isn’t, it’s a primitive value, consult my blog post on categorizing values for details). This is a bug and one that unfortunately can’t be fixed, because it would break existing code. Let’s explore the history of this bug.


The dict pattern: objects without prototypes are better maps

Using objects as maps from strings to values has several pitfalls. This blog post describes a pattern that eliminates some of them.


The JavaScript console API

In most JavaScript engines, there is a global object console with methods for logging and debugging. That object is not part of the language proper, but has become a de facto standard, since being pioneered by the Firebug debugger. Since their main purpose is debugging, the console methods will most frequently be used during development and rarely in deployed code.

This blog post gives an overview of the methods of console.


Safe integers in JavaScript

Update 2014-02-08: Follow-up blog post “What are integers in JavaScript?

JavaScript can only safely represent integers i in the range −253 < i < 253. This blog post examines why that is and what “safely represent” means. It is based on an email by Mark S. Miller to the es-discuss mailing list.