What is the Difference Between null and undefined in JavaScript?
🆚 Go to Comparative Table 🆚In JavaScript, null
and undefined
both represent the absence of a meaningful value, but they have different meanings and use cases:
- Null:
- Represents an intentional empty or non-existent value.
- Is assigned to a variable, indicating that the variable has no value.
- Is an object, and when assigned to a variable, it represents no value.
null
is not strictly equal toundefined
(null !== undefined
), but they are loosely equal (null == undefined
).- Undefined:
- Represents the value of a variable that has not yet been initialized or assigned.
- Indicates that the variable does not exist in the compiler.
- Is a global object.
- Can be used to differentiate between
null
andundefined
usingisNaN()
.
Some key differences between null
and undefined
include:
null
is an assigned value, indicating that the variable has no value, whileundefined
represents a variable that has not yet been assigned a value.null
is an object, whereasundefined
is a global object.- When performing arithmetic operations,
null
is converted to 0, whileundefined
is converted to NaN.
In summary, null
is used to represent an intentional empty value, while undefined
represents a variable that has not yet been assigned a value. It is essential to understand the difference between null
and undefined
to write efficient and error-free JavaScript code.
On this pageWhat is the Difference Between null and undefined in JavaScript? Comparative Table: null vs undefined in JavaScript
Comparative Table: null vs undefined in JavaScript
The main difference between null
and undefined
in JavaScript is:
null
implies that the property exists but does not have a value.undefined
implies that the property itself does not exist.
Here is a table summarizing the differences between null
and undefined
in JavaScript:
Feature | null | undefined |
---|---|---|
Data Type | Object | Undefined |
typeof Operator | "object" | "undefined" |
Arithmetic Operations | When used in arithmetic operations, null is converted to 0 | When used in arithmetic operations, undefined results in NaN (Not a Number) |
Assignment | Null is an empty value or a blank value | Undefined means the variable has been declared, but its value has not been assigned |
In most practical cases, both null
and undefined
denote empty values and carry no information.
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