Why is 0 == "" in JavaScript?

[gappodi@gmail.com]

Why is
0 == "" in JavaScript

Since "A" + 0 != "A" + ""

thank you.
Gap

[Evertjan.]

Re: Why is 0 == "" in JavaScript?

wrote on 21 mrt 2008 in comp.lang.javas cript:

Why is
0 == "" in JavaScript

because

var result = 0 == "";

is not the same as

var result = 0 === "";

==========

With:

var result = 0 == "";

both being near equivalent to false,
and


var result = false == false;

results in true.


--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

[Stevo]

Re: Why is 0 == "" in JavaScript?

gappodi@gmail.c om wrote:

Why is
0 == "" in JavaScript
>
Since "A" + 0 != "A" + ""

Well, "A"+0 is "A0".

As for 0 == "", that's all done to automatic type conversions and the
fact that javascript considers false, 0, "", undefined all as false, and
the rest as true. So 0 is false and "" is false, therefore 0==""

[Douglas Crockford]

Re: Why is 0 == "" in JavaScript?

gappodi@gmail.c om wrote:

Why is
0 == "" in JavaScript
>
Since "A" + 0 != "A" + ""

Mistakes were made.

[Rick Merrill]

Re: Why is 0 == "" in JavaScript?

Thomas 'PointedEars' Lahn wrote:

gappodi@gmail.c om wrote:

>Why is
>0 == "" in JavaScript

>
Steps of evaluation (cf. ECMAScript Ed. 3 Final, sections 11.9.1 to 11.9.3):
>
0 == ""
+0 == +0
true
>

>Since "A" + 0 != "A" + ""

>
"A" + 0 != "A" + ""
!("A" + +0 == "A" + "")
!("A" + "0" == "A" + "")
!("A0" == "A")
!(false)
true
>
>
PointedEars

i think i see your answer to the OP is correct,
but how do you explain the apparent contradiction
0 == ""
AND
0 == "0"

?

[Thomas 'PointedEars' Lahn]

Re: Why is 0 == "" in JavaScript?

Rick Merrill wrote:

Thomas 'PointedEars' Lahn wrote:

>gappodi@gmail.c om wrote:

>>Why is
>>0 == "" in JavaScript

>Steps of evaluation (cf. ECMAScript Ed. 3 Final, sections 11.9.1 to 11.9.3):
>>
> 0 == ""
> +0 == +0
> true
>>

>>Since "A" + 0 != "A" + ""

> "A" + 0 != "A" + ""
> !("A" + +0 == "A" + "")
> !("A" + "0" == "A" + "")
> !("A0" == "A")
> !(false)
> true
>[...]

Please trim your quotes, do not quote signatures unless referring directly
to them.

i think i see your answer to the OP is correct,
but how do you explain the apparent contradiction
0 == ""
AND
0 == "0"

What is perceived as a contradiction by the OP and you here is ignoring that
string concatenation also involves type conversion.


PointedEars
--
var bugRiddenCrashP ronePieceOfJunk = (
navigator.userA gent.indexOf('M SIE 5') != -1
&& navigator.userA gent.indexOf('M ac') != -1
) // Plone, register_functi on.js:16

[Joost Diepenmaat]

Re: Why is 0 == "" in JavaScript?

Rick Merrill <rick0.merrill@ gmail.comwrites :

i think i see your answer to the OP is correct,
but how do you explain the apparent contradiction
0 == ""
AND
0 == "0"

That's not a contradiction, that's just type conversion.

See section 11.8.5 of the emacascript 262 specs:

The Abstract Equality Comparison Algorithm

The comparison x == y, where x and y are values, produces true or
false. Such a comparison is performed as follows:

1. If Type(x) is different from Type(y), go to step 14.

[ snip ]

14. If x is null and y is undefined, return true.
15. If x is undefined and y is null, return true.
16. If Type(x) is Number and Type(y) is String,
return the result of the comparison x == ToNumber(y).
^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^
[ snip ]

ToNumber("0") and ToNumber("") both evaluate to 0.


--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/

[Thomas 'PointedEars' Lahn]

Re: Why is 0 == &quot;&quot; in JavaScript?

Joost Diepenmaat wrote:

See section 11.8.5 of the emacascript 262 specs:

It is ECMA-262 or ECMAScript, not both. Otherwise you are correct.


PointedEars
--
var bugRiddenCrashP ronePieceOfJunk = (
navigator.userA gent.indexOf('M SIE 5') != -1
&& navigator.userA gent.indexOf('M ac') != -1
) // Plone, register_functi on.js:16