In JavaScript, <code>null</code> and <code>undefined</code> are both special values that represent absence or lack of a meaningful value, but they have different meanings.
<code>undefined</code> means that a variable has been declared but has not been assigned a value, or that a property or object does not exist. It is also returned when you try to access a nonexistent object property or function argument.
For example:
<pre><code class="lang-javascript">let x;
console.log(x); // prints undefined

function example(y) {
 console.log(y);
}
example(); // prints undefined
</code></pre>
<code>null</code>, on the other hand, is an intentional absence of any object value. It is used to indicate that a variable, object property or argument should have no value or be empty.
For example:
<pre><code class="lang-javascript">let x = null;
console.log(x); // prints null

let person = {
 name: 'John',
 age: null
};
console.log(person.age); // prints null
</code></pre>
So in summary, <code>undefined</code> means a variable is declared but not assigned a value, or a property or object does not exist, while <code>null</code> represents an intentional absence of any object value.

In JavaScript, `null` and `undefined` are both special values that represent absence or lack of a meaningful value, but they have different meanings.

`undefined` means that a variable has been declared but has not been assigned a value, or that a property or object does not exist. It is also returned when you try to access a nonexistent object property or function argument.

For example:

```javascript
let x;
console.log(x); // prints undefined

function example(y) {
  console.log(y);
}
example(); // prints undefined
```

`null`, on the other hand, is an intentional absence of any object value. It is used to indicate that a variable, object property or argument should have no value or be empty.

For example:

```javascript
let x = null;
console.log(x); // prints null

let person = {
  name: 'John',
  age: null
};
console.log(person.age); // prints null
```

So in summary, `undefined` means a variable is declared but not assigned a value, or a property or object does not exist, while `null` represents an intentional absence of any object value.

What is difference between null and undefined in javascript