What is actually Null?

Question

I don't know if I am asking a valid question or not, but I am curious why PHP, JavaScript, Python interpret null differently

Javascript :

console.log(null === 0); // Outputs false
console.log(null + 1); //Outputs 1 , why ? if null isn't equal to zero

PHP

var_dump(null === 0);
// outputs boolean false

var_dump(null + 1);
// outputs int 1, why if null being not equals to zero ?

Python :

>>None == 0
>>false

Since python None is singleton object, so addition to its gives the error

TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'

Curios about how other language interpret NULL ? And what it should be ? And if Null isn't equals to Zero , why doing a addition on it , it behaves like Zero ?

possible duplicate of [Why is null an object and what's the difference between null and undefined?](http://stackoverflow.com/questions/801032/why-is-null-an-object-and-whats-the-difference-between-null-and-undefined) — scytale, Aug 25 '15 at 10:08
php and javascript are notorious for their "interesting" implementations of null. Python's `None` is a singleton. — scytale, Aug 25 '15 at 10:10
If you convert any non-numeric value to int (or any other numeric data type) will result in 0. — Charlotte Dunois, Aug 25 '15 at 10:13
`var_dump(null === 0);` is false not true, `var_dump(null == 0);` is true — Jan.J, Aug 25 '15 at 10:15
As of JS null + 1, JS ducktypedly autocast any value based on the operation, the parameters type, and their order as well. — Szabolcs Páll, Aug 25 '15 at 10:16
Language design and divergent typecasting rules. Comparing NULL implementation and behaviour across multiple languages doesn't make much sense. — mario, Aug 25 '15 at 10:45
@mario out of curiosity , hope in SO we are allowed to ask such type of questions ? Or have to abide by strict rules & conventions? — Dimag Kharab, Aug 25 '15 at 10:47
A variable is NULL if it has no value, and points to nowhere in memory. — Soorajlal K G, Aug 25 '15 at 10:51
Higher level language design questions can still be on-topic, of couse. But this one is a bit too broad IMO, perhaps even misleading if someone googles for the wrong keywords. — mario, Aug 25 '15 at 10:51

Jan.J · Answer 1 · 2015-08-25T10:26:40.963

2

You can look at type comparison tables of each language to get some understanding. Here are tables for 3 languages you listed:

And then you should check how null (or None) are casted to other types.

For PHP:

(int)null is 0
(string)null is '' (empty string)

For JS:

null + 0 is 0, null + 1 is 1, but parseInt(null) is NaN
null + '' is 'null' and String(null) is 'null'

Can't check it for Python right now. But you see why it behaves like that in PHP and JS. The reasons behind this differences are probably more complicated.

edited Aug 25 '15 at 10:26

answered Aug 25 '15 at 10:12

Jan.J

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Well buddy I wanted to know what we really consider NULL as ? – Dimag Kharab Aug 25 '15 at 10:14
@n01ze then you'll probably have to explain what *"what we really consider NULL as ?"* actually means – jonrsharpe Aug 25 '15 at 11:00
@jonrsharpe yes u r totally correct, I agree with you on this – Dimag Kharab Aug 25 '15 at 11:03

What is actually Null?

1 Answers1