Simplifying Data Manipulation with Computed Properties in Vue 3

In Vue.js, computed properties are properties that are derived from the state of the application and are calculated based on other data properties. Computed properties are useful when you want to perform calculations or apply some logic to your data before using it in your templates.

Step 1: Setting up a Vue 3 project

Before we dive into computed properties, let’s make sure you have a Vue 3 project set up. You can use the Vue CLI or a boilerplate project to get started.

Step 2: Creating a Vue component

Create a new Vue component or open an existing one where you want to use computed properties. For this tutorial, let’s assume you have a component called MyComponent.

Step 3: Define data properties

Inside your component’s data option, define the data properties that you’ll be using for your computed properties. These properties will serve as the basis for your calculations or logic.

data() {
  return {
    firstName: 'John',
    lastName: 'Doe',
  };
},

Step 4: Define computed properties

Below the data option, define your computed properties using the computed option. Computed properties are defined as functions that return a value based on the data properties.

computed: {
  fullName() {
    return this.firstName + ' ' + this.lastName;
  },
},

In the above example, we define a computed property called fullName that concatenates the firstName and lastName data properties.

Step 5: Use computed properties in templates

You can now use the computed property in your template by referencing it as if it were a regular data property.

<template>
  <div>
    <p>First Name: {{ firstName }}</p>
    <p>Last Name: {{ lastName }}</p>
    <p>Full Name: {{ fullName }}</p>
  </div>
</template>

The fullName computed property will automatically update whenever the firstName or lastName data properties change.

Step 6: Computed property caching

By default, computed properties in Vue 3 are cached. This means that if the underlying data properties (e.g., firstName or lastName) haven’t changed, Vue will return the cached value of the computed property instead of recomputing it. This improves performance by avoiding unnecessary calculations.

Step 7: Using setter functions (optional)

Computed properties can also have setter functions, allowing you to update the underlying data properties based on the computed value. To define a setter, you need to provide an object instead of a simple function when defining the computed property.

computed: {
  fullName: {
    get() {
      return this.firstName + ' ' + this.lastName;
    },
    set(value) {
      const [firstName, lastName] = value.split(' ');
      this.firstName = firstName;
      this.lastName = lastName;
    },
  },
},

In the above example, setting the fullName computed property will update the firstName and lastName data properties accordingly.

That’s it! You’ve learned how to use computed properties in Vue 3. Computed properties are a powerful feature that allows you to perform complex calculations or apply logic to your data in a declarative way, making your code more readable and maintainable.

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