Why (null == false) and (null == true) both return false?
The value null
is a JavaScript literal represents an "empty" value or "undefined". null
is one of JavaScript's primitive values. It is neither equal to boolean true
nor equal to boolean false
because it's value is undefined. The value of null
is more inclined towards false even though it is not false
. That's why it's called "falsey" operators and an if (var) { }
block does not get executed when var
is null
.
This is because the Abstract Equality Comparison Algorithm requires that if Type(x)
or Type(y)
is a Boolean in the expression x == y
then the Boolean value should be coerced to a number via ToNumber
, which converts true
to 1 and false
to +0
.
This means that any comparison of true == something
or something == true
results in 1 == something
or something == 1
(replacing true
and 1
with false
and +0
for false
).
The Null type does not compare as equal to either 1 or +0 (in fact, null is only comparable to undefined
in the Abstract Equality Comparison Algorithm).
There is a detailed discussion of all of the different kinds of equality in JavaScript on MDN that is well worth looking at if you want to know more.
However, if you coerce null
to a number it is coerced to +0
so +null == false
actually returns true
.
Answer : There no relative aspect between null and boolean.
MDN Source:-
The value null is a literal (not a property of the global object like undefined can be). In APIs, null is often retrieved in place where an object can be expected but no object is relevant. When checking for null or undefined beware of the differences between equality (==) and identity (===) operators (type-conversion is performed with the former).
// foo does not exist, it is not defined and has never been initialized: > foo "ReferenceError: foo is not defined" // foo is known to exist now but it has no type or value: > var foo = null; foo "null"
Difference between null and undefined
typeof null // object (bug in ECMAScript, should be null) typeof undefined // undefined null === undefined // false null == undefined // true
JavaScript | MDN
Adding to the current discussion. null >= false
returns true
.
I believe that it is because this is interpreted as !(null < false)