Nuxt.jsで必要なTypeScriptの型定義

index.d.ts

import Vue from 'vue'
import {Store} from 'vuex'
import VueRouter, {Route} from 'vue-router'
import {MetaInfo} from 'vue-meta'
import {Snackbar, Toast} from 'buefy'

interface ErrorParams {
  statusCode?: string
  message?: string
}

// Ref. https://nuxtjs.org/api/context
interface NuxtContext {
  app: Vue
  isStatic: boolean
  isDev: boolean
  isHMR: boolean
  route: Route
  store: Store<any>
  env: object
  query: Route['query']
  nuxtState: object
  req: Request
  res: Response
  params: Route['params']
  redirect(path: string, query?: Route['query']): void
  redirect(status: number, path: string, query?: Route['query']): void
  error(params: ErrorParams): void
  beforeNuxtRender({Conmponents, nuxtState}: any): void
}

declare module 'vue/types/options' {
  interface ComponentOptions<V extends Vue> {
    layout?: string
    middleware?: string | String[]
    scrollToTop?: boolean
    transition?: string | object | Function
    head?(): MetaInfo
    fetch?(context: NuxtContext): void
    asyncData?(context: NuxtContext): void
    validate?(context: NuxtContext): boolean
  }
}

declare module 'vue/types/vue' {
  interface Vue {
    $router: VueRouter
    $route: Route
    $snackbar: typeof Snackbar
    $toast: typeof Toast
    $copyText(text: string, container?: any): Promise<Event>
  }
}