JavaScript: How '' == '0' // false and 0 == '' //true?

Question

I am curious how

'' == '0'  // false

left side is a blank string and right side has string with value 0 so its fine its is false.

But

0 == ''    // true

how blank string equals to zero, both are typed different as well as value.

similar

false == 'false'   // false

left is false , but we are not equating (===) type of value , its just has value false so it should be true ? but why it is false.

Could we explain the same ?

Your first two snippets are not symmetrical in the first place. — Frédéric Hamidi, Aug 18 '15 at 09:33
related : http://stackoverflow.com/questions/19839952/all-falsey-values-in-javascript — Hacketo, Aug 18 '15 at 09:36
@ huan son : rarely saw such "stupid" way of answering question. No offense — Mayank, Aug 18 '15 at 09:39
@For -ve: I did research , but output is something confusing. don't have exact answer for the same. not much concern about -ve reputation if get better explanation. Thanks :) — Mayank, Aug 18 '15 at 09:57

score 1 · Answer 1 · answered Aug 18 '15 at 09:36

1

The left operand is of the type Number. The right operand is of the type String. In this case, the right operand is coerced to the type Number:

0 == Number('')
which results in

0 == 0

answered Aug 18 '15 at 09:36

nitin

Starfish · Answer 2 · 2015-08-18T09:54:55.113

0

The following values are always falsy:

I found a nice table explaining what works and what not with the == operator.

Here is the link to the tables also containing === and if().

edited Aug 18 '15 at 09:54

answered Aug 18 '15 at 09:34

Starfish

Just because something is falsy does not explain the rules used when the `==` operator is applied. – zerkms Aug 18 '15 at 09:39
"The empty string is a falsy value, the string containing 0 is not the integer 0 and not empty so the string is true" --- this is wrong. – zerkms Aug 18 '15 at 09:40
"0 (zero) is a falsy value. An empty string ('') is a falsy value too" --- this is wrong as well. – zerkms Aug 18 '15 at 09:40
1

Guys, please **STOP** trying to guess, check the specification **BEFORE** you give answer about language behaviour. Thank you for saving our time. – zerkms Aug 18 '15 at 09:40
An empty string and an integer 0 is a falsy value. You forgot we are comparing with 2 equal signs, not 3. The 3rd equals sign compares the type too. In this case it doesn't. – Starfish Aug 18 '15 at 09:41
Please check and make sure you understand the link http://es5.github.io/#x11.9.3 **before** you continue this useless discussion. What you use as an argument is just nonsense. – zerkms Aug 18 '15 at 09:42
And now it does not address the question in any way. The question was why `==` operator behaves like that. Whereas your answer mentions some term that is not directly relevant to that operator. – zerkms Aug 18 '15 at 09:47

2 Answers2