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What is the difference between null and undefined in JavaScript?
Asked on Jan 20, 2026
Answer
In JavaScript, "null" represents an intentional absence of any object value, while "undefined" indicates that a variable has been declared but not yet assigned a value.
// Example of undefined
let a;
console.log(a); // Output: undefined
// Example of null
let b = null;
console.log(b); // Output: nullAdditional Comment:
✅ Answered with JavaScript best practices.- "undefined" is the default value for variables that have been declared but not initialized.
- "null" is an assignment value that can be used to represent no value or an empty object reference.
- Both "null" and "undefined" are falsy values, meaning they evaluate to false in a boolean context.
- Use "null" when you want to explicitly indicate that a variable should be empty.
- Use "undefined" to check if a variable has not been assigned a value.
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