Neuer Kurs! Jeder Programmierer sollte generative KI lernen!
Kostenlose Lektion ausprobieren0
How is this possible that null and undefined is not equal?
Please anyone help me to this issue Why that null and undefined is not equal?
4 Antworten
+ 5
null and undefined are two distinct types with distinct values, and therefore not equivalent. Specifically, null is a value that signifies the intentional absence of any object value. It is assigned to a variable to indicate that it is intentionally empty, and is recognized as a special keyword in JavaScript treated as a primitive value. Conversely, undefined is a primitive value assigned to a variable when it has not been assigned any value or when a function fails to return a value. Although both null and undefined signify the absence of a value, they bear distinct connotations and thus are not considered equal to each other.
+ 4
For example:
var x = null;
var y = undefined;
console.log(x == y); // true
console.log(x === y); // false
the first comparison x == y returns true because the double equals operator == performs type coercion, which converts null to undefined, making both variables equal. However, the second comparison x === y returns false because the triple equals operator === does not perform type coercion, and the variables have different types and values.
+ 2
But they *are* equal,, insofar as (null == undefined) evaluates to true.
Null === undefined is false because for some reason null is an object in JS, whereas undefined is of undefined type.
+ 2
Remember that === checks also the datatype.
Null is an object and underfined is not an object. So the expression is false.