In JavaScript, understanding the distinction between null and undefined is crucial for writing robust and bug-free code. Both are primitive values, but they serve different purposes and contexts within the language.

Syntax Examples of Null and Undefined in JavaScript

Undefined: Represents a variable that has been declared but has not been assigned a value.

let x;
console.log(x); // Output: undefined

Null: Represents an intentional absence of any object value.

let y = null;
console.log(y); // Output: null

References to Null and Undefined in JavaScript

JavaScript has specific behaviors for handling both null and undefined values

let z;

console.log(z); // Output: undefined

let obj = {
  prop: null
};

console.log(obj.prop);

undefined is practical when the value is not existent, while null is practical in the sense that the value is there because we know it’s not there. The user is undefined until we fetch them, and the user becomes null if the server returned no user.

References

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Last Update: July 27, 2024

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