Menu
×
   ❮   
HTML CSS JAVASCRIPT SQL PYTHON JAVA PHP HOW TO W3.CSS C C++ C# BOOTSTRAP REACT MYSQL JQUERY EXCEL XML DJANGO NUMPY PANDAS NODEJS R TYPESCRIPT ANGULAR GIT POSTGRESQL MONGODB ASP AI GO KOTLIN SASS VUE DSA GEN AI SCIPY AWS CYBERSECURITY DATA SCIENCE
     ❯   

Vue Tutorial

Vue HOME Vue Intro Vue Directives Vue v-bind Vue v-if Vue v-show Vue v-for Vue Events Vue v-on Vue Methods Vue Event Modifiers Vue Forms Vue v-model Vue CSS Binding Vue Computed Properties Vue Watchers Vue Templates

Scaling Up

Vue Why, How and Setup Vue First SFC Page Vue Components Vue Props Vue v-for Components Vue $emit() Vue Fallthrough Attributes Vue Scoped Styling Vue Local Components Vue Slots Vue v-slot Vue Scoped Slots Vue Dynamic Components Vue Teleport Vue HTTP Request Vue Template Refs Vue Lifecycle Hooks Vue Provide/Inject Vue Routing Vue Form Inputs Vue Animations Vue Animations with v-for Vue Build Vue Composition API

Vue Reference

Vue Built-in Attributes Vue Built-in Components Vue Built-in Elements Vue Component Instance Vue Directives Vue Instance Options Vue Lifecycle Hooks

Vue Examples

Vue Examples Vue Exercises Vue Quiz Vue Server Vue Certificate

Vue Computed Properties

Computed properties are like data properties, except they depend on other properties.

Computed properties are written like methods, but they do not accept any input arguments.

Computed properties are updated automatically when a dependency changes, while methods are called on when something happens, like with event handling for example.

Computed properties are used when outputting something that depends on something else.

Computed Properties are Dynamic

The big advantage with a computed property is that it is dynamic, meaning it changes depending on for example the value of one or more data properties.

Computed properties is the third configuration option in the Vue instance that we will learn. The first two configuration options we have already looked at are 'data' and 'methods'.

As with 'data' and 'methods' computed properties also has a reserved name in the Vue instance: 'computed'.

Syntax

const app = Vue.createApp({
  data() {
    ...
  },
  computed: {
    ...
  },
  methods: {
    ...
  }
})

Computed Property 'yes' or 'no'

Let's say we want a form to create items in a shopping list, and we want to mark if a new item is important or not. We could add a 'true' or 'false' feedback when the checkbox gets checked, like we have done in an example before:

Example

An input element is made dynamic so that the text reflects the status.

<input type="checkbox" v-model="chbxVal"> {{ chbxVal }}
data() {
  return {
    chbxVal: false
  }
}
Try it Yourself »

However, if you you ask someone if something is important, they will most likely answer 'yes' or 'no' instead of 'true' or 'false'. So to make our form more fitting with normal language (more intuitive) we should have 'yes' or 'no' as feedback on the checkbox instead of 'true' or 'false'.

And guess what, a computed property is a perfect tool to help us with that.

Example

With a computed property 'isImportant' we can now customize the text feedback to the user when the checkbox is toggled on and off.

<input type="checkbox" v-model="chbxVal"> {{ isImportant }}
data() {
  return {
    chbxVal: false
  }
},
computed: {
  isImportant() {
    if(this.chbxVal){
      return 'yes'
    }
    else {
      return 'no'
  }
}
Try it Yourself »

Computed Properties vs. Methods

Computed properties and methods are both written as functions, but they are different:

  • Methods runs when called from HTML, but computed properties updates automatically when a dependency change.
  • Computed properties are used the same way we use data properties, but they are dynamic.

Vue Exercises

Test Yourself With Exercises

Exercise:

Provide the correct code so that the 'isImportant' computed property is shown on the screen.

<div id="app">
  <form>
    <p>
      Important item?
      <label>
         <input type="checkbox" v-model="chbxVal"> 
         
      </label>
    </p>
  </form>
</div>

<script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
<script>
  const app = Vue.createApp({
    data() {
      return {
        chbxVal: false
      }
    },
    : {
      isImportant() {
        if(this.chbxVal){
          return 'yes'
        }
        else {
          return 'no'
        }
      }
    }
  })
 app.mount('#app')
</script>

Start the Exercise



×

Contact Sales

If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail:
sales@w3schools.com

Report Error

If you want to report an error, or if you want to make a suggestion, send us an e-mail:
help@w3schools.com

W3Schools is optimized for learning and training. Examples might be simplified to improve reading and learning. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using W3Schools, you agree to have read and accepted our terms of use, cookie and privacy policy.

Copyright 1999-2024 by Refsnes Data. All Rights Reserved. W3Schools is Powered by W3.CSS.