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What is the difference between null and undefined in JavaScript?
Asked on May 23, 2026
Answer
In JavaScript, "null" is an assignment value representing the intentional absence of any object value, while "undefined" indicates that a variable has been declared but not assigned a value. Here's a simple example to illustrate the difference:
// 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 used when you want to explicitly indicate that a variable should have no value.
- Both "null" and "undefined" are falsy values, meaning they evaluate to false in a Boolean context.
- Use "=== null" and "=== undefined" to check for these values explicitly, as "==" may lead to unexpected results due to type coercion.
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