Comments on: Truthy and Falsy: When All is Not Equal in JavaScript

By: Craig Buckler

Craig Buckler — Thu, 02 Jul 2009 12:56:27 +0000

@Robert Katić
Yep – you’re right. Well spotted – I’ve fixed the article. It makes you wonder why undefined and null were both implemented. The difference is fairly subtle and uninitialized variables could have been set to null.

@Jaffa The Cake
Certainly !!([]) returns true. I’m not surprised that ([]==true) fails, but then you’d expect ([]==false) to fail too?!

It just goes to show how careful you need to be. It would not surprise me if there were inconsistencies between browsers too.

By: Robert Katić

Robert Katić — Thu, 02 Jul 2009 12:14:26 +0000

(undefined == null) gives true.

By: Jaffa The Cake

Jaffa The Cake — Thu, 02 Jul 2009 10:23:50 +0000

The true & false thing gets a bit weird with objects and arrays…

if ( [] ) {
// this runs
}

if ( [] == true ) {
// this does not run
}

if ( [] == false ) {
// this does run
}

Jake.

By: Anonymous

Anonymous — Wed, 01 Jul 2009 01:09:54 +0000

I thought === was a php specific operator. Learn something new everyday :)

By: lotrgamemast

lotrgamemast — Tue, 30 Jun 2009 21:39:46 +0000

I’ve gotten into the habbit of always using the strict compares when writing javascript.

It also catches stuff like:

if ( “0″ == 0 ) // true
if ( “0″ === 0 ) // false

So you know you’re getting the right data type.

By: Balaji

Balaji — Tue, 30 Jun 2009 21:13:22 +0000

“Great article! Thanks for taking the time to explain Truth and Falsy values.