Why does (true > null) always return true in JavaScript?

Question

Can some tell me why the following code returns true in JavaScript?

console.log(true > null); //returns true

Yes because null is a falsy expression (then *false*) and comparison operator will convert it to a _number_ (then true = 1 and false = 0). — Adriano Repetti, Jul 23 '12 at 14:41
http://stackoverflow.com/questions/801032/null-object-in-javascript — xkeshav, Jul 23 '12 at 14:42
@elclanrs I'm lazy to write a complete answer with references to JavaScript standard (for who is interested just start from section 11.8.2). — Adriano Repetti, Jul 23 '12 at 14:46

score 12 · Accepted Answer · answered Jul 23 '12 at 14:44

12

null is like false in this case, wich is 0 as a number. true is 1 as a number.

1 is bigger (>) than 0.

answered Jul 23 '12 at 14:44

oezi

51,017
10
98
115

Thanks for the answer. I was wondering why is null === 0 false? Then I realised it needs to be coerced. So for those who need absolute proof, try + null === 0 which evaluates to true proving that indeed null is coerced to 0. Just thought this might help others. – GrantVS Oct 15 '13 at 11:16

score 7 · Answer 2 · answered Jul 23 '12 at 14:44

They are converted to numbers, null gives 0 and true gives 1

http://ecma-international.org/ecma-262/5.1/#sec-11.8.5

If it is not the case that both Type(px) is String and Type(py) is String, then

Let nx be the result of calling ToNumber(px). Because px and py are primitive values evaluation order is not important.

Let ny be the result of calling ToNumber(py).

Number(null) //0
Number(true) //1

score 2 · Answer 3 · answered Jul 23 '12 at 14:44

2

May be because true = 1 where null = 0

answered Jul 23 '12 at 14:44

Mahmoud Abdelaziz

117
1
1
9

score 2 · Answer 4 · answered Jul 23 '12 at 14:45

JavaScript does a lot of type coercion in the background and a lot of the results you'll find aren't useful (see http://wtfjs.com/).

In this case, true which is coerced as 1 is greater than null which is coerced to 0. Since 1 is greater than 0 the result is true.

If one of the operands is Boolean, the Boolean operand is converted to 1 if it is true and +0 if it is false.

From the MDN.

score 1 · Answer 5 · answered Jul 23 '12 at 14:49

What's happening behind is that the relational operators ( > in this case) perform type coercion before doing the comparison. When doing the ToPrimitive, true gets coerced to a 1, and null to a 0. You can check details here of how the operators actually work here

score 0 · Answer 6 · answered Jul 23 '12 at 14:45

0

The code is incorrect, you need to do:

console.log(true > typeof null);

answered Jul 23 '12 at 14:45

FabianoLothor

2,752
4
25
39

score 0 · Answer 7 · answered Jul 23 '12 at 14:48

0

The compare operator ">" forces both it's left and right side to be converted to numbers. Number(true) is 1, Number(null) is 0, so what is in the paranthesis is taken as "1>0", which is always true in result.

answered Jul 23 '12 at 14:48

Michael Besteck

2,415
18
10

Why does (true > null) always return true in JavaScript?

7 Answers7

Linked