Javascript confusing syntax inconsistence for null, instanceof and typeof?

Question

var obj = {};
typeof obj; // returns \"object\"
obj instanceof Object // return true

typeof null // returns \"object\"
null instanceof Object // returns false
         


        

Answer 1

That's a common bug of ECMAScript.

null is not an object, it's a primitive value.(So you can't modify it like adding properties to it)

typeof null should return null

typeof null // object (bug in ECMAScript, should be null)

typeof undefined // undefined

null === undefined // false

null == undefined // true

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/null

EDITED

It's not available to see though

Changed 3 weeks ago by brendan

You know, this all came about because of rushing in early May 1995, which led to a leak of type tag representation shared by null and object types. But null means "no object", so it didn't raise hackles until it was too late to fix in Netscape 2, and after that we were loath to "fix" it and "break the web". That argument only applies more in degree of web population now. We have other fish to fry. This one was has been swallowed already. Let's not change typeof null for ES4 and work on more vital issues.

http://web.archive.org/web/20071110193102/http://bugs.ecmascript.org/ticket/250

also check this answer

Why is null an object and what's the difference between null and undefined?