Javascript quirks

Question

I was playing around with Chrome's Javascript console recently, and I discovered this oddity:

[] == true
false
[0] == true
false
[0] == []
false

This doesn't seem to make any sense at first glance (false != false), but I think the real reasoning lies in the polymorphism of the == operator. Comparing an array to a boolean isn't the same thing as comparing an array to another array.

With that said, what are other Javascript quirks you've discovered?

Haha, of course there's a whole site dedicated to making fun of Javascript. — Zach Rattner, Apr 01 '11 at 00:56
Open-ended list questions should be avoided, as per the faq: http://stackoverflow.com/faq#dontask — Yi Jiang, Apr 01 '11 at 01:06
[The Garden](http://bonsaiden.github.com/JavaScript-Garden/). It's about quirks. — Raynos, Apr 01 '11 at 01:08
In JavaScript, booleans are compared by value and arrays are compared by reference. So while `[0] == true` is false, `[0] == false` is true, and `[1] == true` is true. JavaScript is calling `valueOf()` on the array objects. — Paul, Apr 01 '11 at 01:09

score 3 · Answer 1 · edited May 23 '17 at 12:16

3

I asked a similar question on equality transitivity recently and Alex provided a really good answer...

Alex's answer

I hope that helps.
Hristo

edited May 23 '17 at 12:16

Community

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answered Apr 01 '11 at 01:02

Hristo

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score 2 · Answer 2 · answered Apr 01 '11 at 01:03

2

Look into truthy and falsey javascript. It's seriously called that.

answered Apr 01 '11 at 01:03

Justin Thomas

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Javascript quirks

2 Answers2