Property 'XXX' does not exist on type 'CombinedVueInstance<Vue, {}, {}, {}, Readonly<Record<never, any>>>'

I created a vue component with TypeScript, and I'm getting this error in data() and in methods():

Property 'xxx' does not exist on type 'CombinedVueInstance<Vue, {},
{}, {}, Readonly<Record<never, any>>>'.

For example:

33:18 Property 'open' does not exist on type 'CombinedVueInstance<Vue, {}, {}, {}, Readonly<Record<never, any>>>'.
    31 |         methods: {
    32 |             toggle: function () {
  > 33 |                 this.open = !this.open
       |                  ^
    34 |                 if (this.open) {
    35 |                     // Add click listener to whole page to close dropdown
    36 |                     document.addEventListener('click', this.close)

This error also shows any time this.close() is used.

This is the component:

<script lang='ts'>
    import Vue from 'vue';
    import axios from 'axios'
    export default Vue.extend({
        data: function () {
            return {
                open: false
            }
        },
        computed: {
            profilePath: function () {
                return "/user/" + this.$store.state.profile.profile.user.id
            }
        },
        methods: {
            toggle: function () {
                this.open = !this.open
                if (this.open) {
                    // Add click listener to whole page to close dropdown
                    document.addEventListener('click', this.close)
                }
            },
            close: function () {
                this.open = false;
                document.removeEventListener('click', this.close)
            }
        }
    })
</script>

What is causing this error? It seems to still build in development with the errors, but they are causing issues when I deploy to production.

Solution 1:

As mentioned in the Typescript Support section of the Vue documentation:

Because of the circular nature of Vue’s declaration files, TypeScript may have difficulties inferring the types of certain methods. For this reason, you may need to annotate the return type on methods like render and those in computed.

In your case, you should change profilePath: function () { to profilePath: function (): string {

You might come across the same error if you have a render() method that returns a value, without a : VNode annotation.

Solution 2:

This seems to be inexplicably caused by using this.$store to compute the return value of profilePath, combined with the unspecified return type on its declaration.

One workaround is to specify the return type as string:

profilePath: function(): string {

verified with npm run serve and npm run build, using Vue CLI 3.7.0 on macOS Mojave

GitHub demo

Solution 3:

I get below error: Property 'doThisInput' does not exist on type 'CombinedVueInstance<Vue, unknown, unknown, unknown, Readonly<Record<never, any>>>'.

And also doThisClickgave same error.

Solution: i have added declaration to component.

<script lang="ts">
  import Vue from 'vue';

  // Add below code sample to your component
  declare module 'vue/types/vue' {
    interface Vue {
      fields: Field[];
      doThisClick: () => void;
      doThisInput: () => void;
    }
  }

  export default Vue.extend({
    name: 'form-builder',
    data() {
      return {
        fields: [
          {
            name: 'name',
            events: { click: this.doThisClick, input: this.doThisInput },
          },
        ],
      };
    },
    methods: {
      doThisClick(field: Field): void {
        console.log('click', field, event);
      },
      doThisInput(field: Field): void {
        console.log('Input', field, event);
      },
    },
  });
</script>

Solution 4:

For me, the solution was to explicitly define the return value for all computed properties, methods, etc.

So instead of:

myComputedProperty() {
  return this.foo;
},

I had to do

myComputedProperty(): boolean {
  return this.foo;
},

Even though I would expect, that by type inference this shouldn't be necessary