TypeScript has undoubtedly grown in popularity over recent years. More and more developers within the web industry are looking to use static-type languages and with the release of Angular 2 back in 2016, this has only increased the demand for developers who use TypeScript.

When I started writing Angular applications with TypeScript, I thought it was great. I liked static-type checking systems and I liked being able to store the template outside of the TypeScript file, giving me separation from the logic and presentation layers. Unfortunately, I didn't like the fact that Angular requires so much set-up and not to mention the fact you had to do three or four different things to build one component. For me, it was too costly for time.

Prior to this I had used VueJS for building single page applications and I loved it. I always wanted to be able to bring TypeScript to VueJS and so the research began!

Now I found many tutorials that explained how TypeScript could be used with VueJS, but a lot of these were focusing on single file components. Which in my opinion works with using just JavaScript, but I really liked how Angular could store the template in an HTML file.

@Component({
    selector: 'my-dashboard',
    templateUrl: 'dashboard.component.html',
})
export class DashboardComponent {}

When I thought I was out of luck, I found the solution to all of my problems. The amazing VueJS team have recently released Vue CLI 3 - which has made the process of writing TypeScript applications with VueJS so much easier! Let's take a look on how to setup a VueJS application using TypeScript.

Install Vue CLI

The first step is to install Vue CLI, to do this, simply run one of the following commands (depending on what tool you use).

npm install -g @vue/cli
# OR
yarn global add @vue/cli

Once this is done, you can verify that it has installed correctly by running vue --version. It should display something like 3.0.1.

Create a TypeScript project

The new Vue CLI tool allows you to easily create new projects with TypeScript. To get started, simply run vue create my-app. You'll then be asked to choose a preset. Using your arrow keys, choose Manually select features.

Next, you just need to ensure you have selected the TypeScript and Babel options. You can see below that I have also selected some other optional features.

Once you've done this, it will ask you if you would like to use the class-style component syntax. You will want to choose this option.

Then configure the rest of the settings so it should look like the below image.

The Vue CLI tool will now install all of the dependencies and set the project up.

Add Extra Dependencies

To achieve the affect we are after, there are a few extra dependencies that we need to install. You can install these by running one of the following commands.

npm install --save vue-template-loader webpack-stream
# OR
yarn add vue-template-loader webpack-stream

You should now be able to run yarn serve to view your current application.

Using TypeScript classes instead of Single File Components

Next, we want to remove the need for .vue files and instead use TypeScript classes. Within the components directory, you can see there is HelloWorld.vue. We are going to re-create this with a TypeScript class instead.

So firstly, create a new file within the components directory and call it HelloWorld.ts. We'll add the following boilerplate to get started.

import { Component, Vue } from 'vue-property-decorator';

@Component
export default class HelloWorld extends Vue {

}

This gives us a blank component ready to use. The first thing we need to do is have an external .html file for our presentation layer of the component. To do this, create a new file called hello-world.html. You can place this file wherever you want, but for demonstration purposes I will place it in the same folder as our component.

Now we need to copy across the presentation from the HelloWorld.vue component into our new hello-world.html file. So our file should now look like this.

<div class="hello">
    <h1>{{ msg }}</h1>
    <p>
      For guide and recipes on how to configure / customize this project,<br>
      check out the
      <a href="https://cli.vuejs.org" target="_blank" rel="noopener">vue-cli documentation</a>.
    </p>
    <h3>Installed CLI Plugins</h3>
    <ul>
      <li><a href="https://github.com/vuejs/vue-cli/tree/dev/packages/%40vue/cli-plugin-babel" target="_blank" rel="noopener">babel</a></li>
      <li><a href="https://github.com/vuejs/vue-cli/tree/dev/packages/%40vue/cli-plugin-typescript" target="_blank" rel="noopener">typescript</a></li>
    </ul>
    <h3>Essential Links</h3>
    <ul>
      <li><a href="https://vuejs.org" target="_blank" rel="noopener">Core Docs</a></li>
      <li><a href="https://forum.vuejs.org" target="_blank" rel="noopener">Forum</a></li>
      <li><a href="https://chat.vuejs.org" target="_blank" rel="noopener">Community Chat</a></li>
      <li><a href="https://twitter.com/vuejs" target="_blank" rel="noopener">Twitter</a></li>
      <li><a href="https://news.vuejs.org" target="_blank" rel="noopener">News</a></li>
    </ul>
    <h3>Ecosystem</h3>
    <ul>
      <li><a href="https://router.vuejs.org" target="_blank" rel="noopener">vue-router</a></li>
      <li><a href="https://vuex.vuejs.org" target="_blank" rel="noopener">vuex</a></li>
      <li><a href="https://github.com/vuejs/vue-devtools#vue-devtools" target="_blank" rel="noopener">vue-devtools</a></li>
      <li><a href="https://vue-loader.vuejs.org" target="_blank" rel="noopener">vue-loader</a></li>
      <li><a href="https://github.com/vuejs/awesome-vue" target="_blank" rel="noopener">awesome-vue</a></li>
    </ul>
  </div>

So how do we use this template file within our HelloWorld.ts class? The extra dependencies we installed enable us to use another decorator, WithRender. This allows us to import our HTML file and tell our Vue component to use our file for rendering. After adding this to our TypeScript file, it should look like this.

import { Component, Vue } from 'vue-property-decorator';
import WithRender from './hello-world.html';

@WithRender
@Component
export default class HelloWorld extends Vue {

}

Now we need to hook up the Vue Router to use our new TypeScript class instead of the HelloWorld.vue file. To do this, open the views/Home.vue file. Realistically you would also create a TypeScript class for this component as well, but for this guide, we will just edit it.

Within the file, change the import statement to use our TypeScript file instead. So we will change the following line from

import HelloWorld from '@/components/HelloWorld.vue'

to

import HelloWorld from '@/components/HelloWorld.ts';

However, if you now go to your browser, you will see there is an error. In our terminal we get the error:

Cannot find module './hello-world.html'

This is because TypeScript doens't know how to handle .html files. So we need to add a shim file. To do this, within the src folder, create a shims-html.d.ts file. Paste the following code so your file should look like this:

declare module '*.html' {
    import Vue, { ComponentOptions, FunctionalComponentOptions } from 'vue'
    interface WithRender {
        <V extends Vue, U extends ComponentOptions<V> | FunctionalComponentOptions>(options: U): U
        <V extends typeof Vue>(component: V): V
    }
    const withRender: WithRender
    export default withRender
}

Now we need to update our tsconfig.json file so that TypeScript knows to load .html files. Add the following line to the include array: "src/**/*.html". So it should look something like this:

  ...
  "include": [
    "src/**/*.ts",
    "src/**/*.tsx",
    "src/**/*.vue",
    "tests/**/*.ts",
    "tests/**/*.tsx",
    "src/**/*.html"
  ],
  ...

Finally, we need to add some custom webpack configuration in the build process to tell Vue to pass the html file through its template compiler. To do this, within the root of your project create a vue.config.js file and add the following:

module.exports = {
  configureWebpack: {
    module: {
      rules: [
        {
          test: /.html$/,
          loader: "vue-template-loader",
          exclude: /index.html/
        }
      ]
    }
  }
}

Next, we need to restart the compilation process so TypeScript loads our changes. Close the current terminal process and run one of the following commands again.

npm run serve
# OR
yarn serve

You should now see the application loading as it was before, this time it is using the TypeScript class file and the html template file.

One last thing you might notice is that the msg data property is no longer there. So let's add that now.

Within your HelloWorld.ts file, add the following property

public msg: string = 'I am using TypeScript classes with Vue!';

If you now look back at your browser, you should now see this being rendered on the page.

That's all there is to it, you can now build your application using Vue, but using TypeScript classes and html file templates. While some people may disagree with this approach and argue you should only use .vue files, I find this
approach cleaner, especially when some of the files get really long.

This is the first part in a series. Next time I will go deeper into writing VueJS applications with TypeScript and explain methods, data attributes, props, child components and more!

UPDATE

Part two is now available - https://dev.to/georgehanson/building-vue-js-applications-with-typescript-part-two-2808