Difference between Null and Undefined in JavaScript

Both a primitive type and an empty value in JavaScript are referred to as null. The variable that has been marked as null is empty. The variable has been declared but has not yet been given a value if it is undefined.

What is Null?

In English, the word "null" has been used frequently. Literally, it means having no value. Similar to how null in programming has the same meaning.

Null is essentially a variable's assignment value. The variable that has been marked as null is empty.

Any variable that has the value null assigned to it is considered to be empty or blank. It demonstrates that the variable is meaningless. In JavaScript, a null is also an object, and it has no meaning when it is applied to a variable. As JavaScript never changes the value to null, the user must explicitly set the value. Setting an object to null will empty it.

Null is a special value that represents the intentional absence of any object value. It is often used to indicate that a variable or object property does not have a value, or to explicitly reset a variable or object property to no value.

For example:

What is Undefined?

Although there is a small distinction between null and undefined, it is crucial that programmers are aware of it.

Undefined, as the name implies, is defined as "not defined". As a result, when a variable is declared but not given a value, it is said to be undefined.

In contrast to null, JavaScript declares an undefined variable's value to be undefined. At runtime, the variable is generated. When a function parameter is not sent an argument, the default value is assumed to be undefined. Moreover, a function returns undefined when it doesn't produce a value.

Undefined is a primitive value that is automatically assigned to a variable that has been declared but has not been initialized with a value. It is also the default value of function parameters that are not passed a value. For example:

Output

undefined

Some differences of NULL and Undefined

There are various differences between null and undefined. Some main differences between the null and undefined are as follows:

1. Null is an object type, while undefined is a primitive type. However, both are considered falsy values in JavaScript, meaning they will evaluate to false in a Boolean context.

2. The typeof operator can be used to determine whether a value is null or undefined.

For example:

3. When a function does not explicitly return a value, it will return undefined by default.

For example:

4. Undefined can also arise from accessing properties or variables that do not exist.

For example:

5. Both null and undefined can be explicitly assigned to a variable or object property. However, it is generally recommended to use null to represent the absence of a value and to reserve undefined for variables that have not been initialized or for function parameters that are not passed a value.

6. When comparing null and undefined, they are considered equal to each other but not to any other value.

For example:

7. When you attempt to access a property of an object that does not exist, JavaScript will return undefined rather than throwing an error.

8. Null is often used to indicate that an object does not exist or is not available. For example, if a function is expecting an object as an argument but one is not provided, it might return null to indicate that no object was found. However, it's important to note that returning null is a convention rather than a requirement in JavaScript.

9. Undefined is sometimes used to indicate that a value is missing or has not been provided. For example, if a function is expecting an argument but one is not provided, it might use undefined as the default value. Similarly, if a variable has not been initialized with a value, it will have the value undefined.