Vue 3 Computed Property

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In-template expressions are very convenient, but they are really meant for simple operations only. Templates are meant to describe the structure of your view.

Putting too much logic into your templates can make them bloated and hard to maintain. This is why Vue.js limits binding expressions to one expression only. For any logic that requires more than one expression, you should use a computed property. a={{ a }}, b={{ b }}. Here we have declared a computed property b. The function we provided will be used as the getter function for the property vm.b:.

You can open the console and play with the example vm yourself. The value of vm.b is always dependent on the value of vm.a.

You can, the setter will be invoked and vm.firstName and vm.lastName will be updated accordingly. The technical details behind how computed properties are updated are discussed in another section dedicated to the reactivity system. Caught a mistake or want to contribute to the documentation?Edit this page on Github! Editor’s note: This Vue.js and TypeScript tutorial was last updated on 30 April 2021. In this tutorial, we’ll demonstrate how to build a Vue.js app completely in TypeScript.

We’ll highlight some of the benefits of using TypeScript with Vue by building a Vue + TypeScript example app with class-based components, Vuex for state management, lifecycle hooks, and more.

Here’s what we’ll cover during this walkthrough:. Vue.js is an amazing, lightweight, and progressive frontend framework. Since Vue.js is flexible, users are not forced to use TypeScript.

And unlike Angular, older versions of Vue did not have proper support for TypeScript.

For this reason, most Vue applications have historically been written in JavaScript. Vue 3 was released on 18 September 2020. New features shipped with Vue 3 include a built-in composition API, multiple root elements, and, crucially for this tutorial, improved TypeScript support.

For a detailed guide on how to migrate your existing Vue.js projects to Vue 3, check out “Refactoring your Vue 2 apps to Vue 3.”. Now that Vue.js officially supports TypeScript, it’s possible to create TypeScript projects from scratch using Vue CLI.

However, you still need some third-party packages with custom decorators and features to create a true, complete TypeScript application. The official Vue and TypeScript documentation doesn’t include all the information you need to get started. To help paint a fuller picture, we’ll demonstrate how to build a new Vue and TypeScript application using Vue CLI. To add TypeScript to your Vue.js project, start with this line of code:.

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Choose manually select features and configure it as shown below:.

  • Once the project is set up, run the project to test it:.
  • Open localhost:8080 (or the URL your console shows after starting the project), and we can see it running successfully.
  • Open the HelloWorld.vue file from the components directory.
  • For each item below, I’ll show both the TypeScript and JavaScript-equivalent code so you can easily compare the two.
  • Let’s get started!