How do I use computed properties in Vue 3 with the setup script?

How do I use computed properties in Vue 3 with the setup script?

In Vue 3, you can use the computed function from Vue's Composition API. Here's a basic example:

import { ref, computed } from 'vue';

export default {
  setup() {
    const count = ref(0);
    const doubleCount = computed(() => count.value * 2);

    return { count, doubleCount };
  }
};

This creates a reactive count and a computed property doubleCount that automatically updates when count changes.

Can you explain how the reactivity works with computed properties?

Sure! Computed properties in Vue 3 are reactive. They automatically re-evaluate when their dependencies change. In the example, doubleCount depends on count. When count is updated, Vue re-computes doubleCount for you, ensuring that the UI reflects the latest values.

What are the benefits of using computed properties over methods?

Computed properties are cached based on their dependencies, meaning they only re-evaluate when necessary. This makes them more efficient than methods, which run every time the component re-renders. If you need a value that depends on other reactive data, computed properties are the way to go!

Can I use computed properties with props?

Absolutely! You can create computed properties that depend on props. For example, if you receive a price prop, you can create a computed property to apply a discount and return the final price. Just ensure to access the prop within the setup function.