vue/types/test/augmentation-test.ts

import Vue from '../index'

declare module '../vue' {
  // add instance property and method
  interface Vue {
    $instanceProperty: string
    $instanceMethod(): void
  }

  // add static property and method
  interface VueConstructor {
    staticProperty: string
    staticMethod(): void
  }
}

// augment ComponentOptions
declare module '../options' {
  interface ComponentOptions<V extends Vue> {
    foo?: string
  }
}

const vm = new Vue({
  props: ['bar'],
  data: {
    a: true
  },
  foo: 'foo',
  methods: {
    foo() {
      this.a = false
    }
  },
  computed: {
    BAR(): string {
      return this.bar.toUpperCase()
    }
  }
})

vm.$instanceProperty
vm.$instanceMethod()

Vue.staticProperty
Vue.staticMethod()