Property 'x' does not exist on type '{toggle():void}'

Question

I am pretty new to typescript. Now, I have setup nuxt(bridge with typescript) app and created a component named menuIcon as such;

  <div class="container">


    <div class="menu-icon" :class="active ? 'change' : ''" @click="toggle">
      <div class="bar1"></div>
      <div class="bar2"></div>
      <div class="bar3"></div>
    </div>
    <div
      class="overlay"
      :class="active ? 'overlay-slide-right' : 'overlay-slide-left'"
      @click="toggle"
      id="overlay"
    >
    <!-- html contents here -->
    </div>
  </div>
</template>

<script lang="ts">


export default {
  data(){
    const active:boolean=false;
    return{
        active
    }
  },
  methods: {
    toggle():void{
       this.active= !this.active
    },
  },
};
</script>
<style scoped>
/*css contents here*/
}
</style>

It is working in browser but I am seeing the following error in my terminal.

TS2339: Property 'active' does not exist on type '{ toggle(): void; }'.
    41 |   methods: {
    42 |     toggle():void{
  > 43 |        this.active= !this.active
       |             ^^^^^^
    44 |     },
    45 |   },
    46 | };

ERROR in components/MenuIcon.vue:43:27
TS2339: Property 'active' does not exist on type '{ toggle(): void; }'.
    41 |   methods: {
    42 |     toggle():void{
  > 43 |        this.active= !this.active
       |                           ^^^^^^
    44 |     },
    45 |   },
    46 | };

Apparently it's something about typing but I am not sure how to fix it. I would very much appreciate anyone to shed light on me about the issues. Thanks in advance.

Answer 1

The component definition needs to be declared with Vue's defineComponent to enable TypeScript support. Nuxt Bridge recommends using defineComponent from the #app import, although you could also import it from @vue/composition-api. Using the #app alias is preferrable because it includes Nuxt specific types from @nuxtjs/composition-api.

Example:

<script lang="ts">
import { defineComponent } from '#app';
                      
export default defineComponent({
  data() {
    const active:boolean = false;
    return {
      active
    }
  },
  methods: {
    toggle(): void {
      this.active = !this.active
    },
  },
});
</script>

The #app alias is normally setup in .nuxt/tsconfig.json, but I found it's necessary to re-declare it in the root app's tsconfig.json to work in VS Code:

{
  "extends": "./.nuxt/tsconfig.json",
  "compilerOptions": {
    "paths": {
      ⋮
      "#app": [
        "node_modules/@nuxt/bridge/dist/runtime/index"
      ],
    }
  }
}

demo