---
title: "What are computed observables in Knockout.js?"
description: "What are computed observables in Knockout.js?"
author: "Ashutosh Patel"
published: 2024-06-27
updated: 2024-06-27
canonical: https://www.mindstick.com/interview/33929/what-are-computed-observables-in-knockout-js
category: "knockcout js"
tags: ["javascript", "knockout.js", "knockout observables"]
reading_time: 3 minutes
---
# What are computed observables in Knockout.js?
#### Knockout.js Computed Observable
The objects calculated in Knockout.js are unique view objects that update themselves whenever any of the clients changes. It is used to get or calculate values based on other visible or explicit JavaScript attributes in your visualization. Here is a detailed explanation:
## Definition
Computed observables (`ko.computed()`) in Knockout.js are functions that compute a value based on other observables or simple JavaScript properties. They are automatically updated every time a care is due based on changes.
## Example-
```html
Computed observable Example
Knockout.js Computed observable
First Name:
Last Name:
Full Name:
```
**In this example**,
`fullName` is a numeric observable based on `firstName` and `lastName`. Whenever **firstName** or **lastName** changes, `fullName` automatically computed its value (`this.firstName() + ' ' + this.lastName();`).
## Output-
**Also, Read:** [Explain the role of observables and computed observables in Knockout.js?](https://www.mindstick.com/forum/160790/explain-the-role-of-observables-and-computed-observables-in-knockout-js)
## Answers
### Answer by Ashutosh Patel
#### Knockout.js Computed Observable
The objects calculated in Knockout.js are unique view objects that update themselves whenever any of the clients changes. It is used to get or calculate values based on other visible or explicit JavaScript attributes in your visualization. Here is a detailed explanation:
## Definition
Computed observables (`ko.computed()`) in Knockout.js are functions that compute a value based on other observables or simple JavaScript properties. They are automatically updated every time a care is due based on changes.
## Example-
```html
Computed observable Example