# How to iterate over object properties using for...in loop in JavaScript

By Atta Ur Rehman Shah (https://attacomsian.com/about). Published Sep 19, 2022. Topics: JavaScript.
Canonical URL: https://attacomsian.com/blog/javascript-iterate-object-using-for-in-loop

> Learn how to use the for...in loop to iterate over object keys and values in JavaScript.

The simplest way to [iterate over object](https://attacomsian.com/blog/javascript-iterate-objects) keys and values is using the `for...in` loop. This method works in all modern and old browsers, including Internet Explorer 6 and higher.

Here is an example that uses the `for...in` loop to iterate over an object:

```javascript
const user = {
  name: 'John Doe',
  email: 'john.doe@example.com',
  age: 25,
  dob: '08/02/1989',
  active: true
}

// iterate over the user object
for (const key in user) {
  console.log(`${key}: ${user[key]}`)
}

// name: John Doe
// email: john.doe@example.com
// age: 25
// dob: 08/02/1989
// active: true
```

The only problem with `for...in` loop is that it iterates through the properties in the prototype chain. 

Since the objects in JavaScript can inherit properties from their [prototypes](https://attacomsian.com/blog/objects-prototypes-classes-javascript#prototypes), the `for...in` statement will loop through those properties as well.

To exclude prototype properties while looping over an object, you need to explicitly check if the property belongs to the object by using the `hasOwnProperty()` method:

```javascript
for (const key in user) {
  if (user.hasOwnProperty(key)) {
    console.log(`${key}: ${user[key]}`)
  }
}
```