Computed properties in Vue.js 3 are special properties that are derived from other properties in a component. They are calculated on-the-fly and cached for performance, so that their values are updated whenever the source properties change. Computed properties provide an efficient way to manipulate or format data, without changing the original data source.
It provide a way to derive values from other component data, and cache the results for improved performance. They are reactive, meaning that when the source data changes, the computed property value updates automatically. This can simplify your component code and make it easier to manage complex data relationships.
Here's an example to illustrate the concept of computed properties in Vue.js
<template>
<div>
<p>{{ fullName }}</p>
</div>
</template>
<script>
export default {
data() {
return {
firstName: 'John',
lastName: 'Doe'
}
},
computed: {
fullName() {
return this.firstName + ' ' + this.lastName
}
}
}
</script>
In this example, the fullName
computed property is derived from the firstName
and lastName
data properties. The fullName
property is calculated using a getter function, which concatenates the firstName
and lastName
properties.
The fullName
property is used in the template, and its value is displayed in the view. When either the firstName
or lastName
properties change, the fullName
property is automatically re-computed, and the view updates to reflect the change.
Here are some key features and benefits of computed properties in Vue.js 3:
Caching: Computed properties are cached, meaning that their values are only recalculated when one of the source properties changes. This makes them very efficient, especially for complex calculations or data transformations.
Reactivity: Computed properties are reactive, meaning that when the source data changes, the computed property value updates automatically. This makes it easy to maintain consistent, up-to-date data in your component.
Readability: By using computed properties, you can extract complex calculations and data manipulations into reusable, named functions. This makes your component code more readable and easier to maintain.
Easy to use: Computed properties can be accessed just like any other component data, using the component's instance. For example, you can use a computed property in a template, or access its value from another component method.
Getters and setters: Computed properties can have both a getter and a setter function, which allows you to define how the computed property value should be calculated and updated.
Computed properties can be defined in a component using the computed
option. You define the computed properties as properties of an object, where the key is the name of the computed property and the value is a getter function. For example:
computed: {
fullName() {
return this.firstName + ' ' + this.lastName
}
}
In this example, the fullName
computed property is defined as a function that concatenates the firstName
and lastName
properties.
You can use computed properties in your component templates, like any other component data. For example:
<template>
<div>
<p>{{ fullName }}</p>
</div>
</template>
In this example, the fullName
computed property is used in the template, and its value is displayed in the view. When either the firstName
or lastName
properties change, the fullName
property is automatically re-computed, and the view updates to reflect the change.
Computed properties can also have setter functions, which allow you to define how the computed property should be updated when its value is changed. For example:
computed: {
fullName: {
get() {
return this.firstName + ' ' + this.lastName
},
set(value) {
const [firstName, lastName] = value.split(' ')
this.firstName = firstName
this.lastName = lastName
}
}
}
In this example, the fullName
computed property has both a getter and a setter function. The getter function works as before, concatenating the firstName
and lastName
properties. The setter function splits the value
into firstName
and lastName
parts, and updates the corresponding properties.
In conclusion, computed properties are a valuable tool for managing and transforming data in Vue.js. They allow you to derive values from other component data, cache the results for improved performance, and update automatically when the source data changes. Computed properties provide a convenient and efficient way to manipulate and format data, making your component code more readable and easier to maintain. Whether you are working on a small or large project, computed properties can help you keep your data organized and up-to-date, and make it easier to manage complex data relationships.