vue Router 4源码解析：如何创建路由

// 定义 router 参数
import { createRouter, createWebHashHistory } from 'vue-router'

// 创建一个可以被 Vue 应用程序使用的路由实例
export const router = createRouter({
  // 创建一个 hash 历史记录。
  history: createWebHashHistory(),
  // 应该添加到路由的初始路由列表。
  routes: basicRoutes as unknown as RouteRecordRaw[],
  scrollBehavior: () => ({ left: 0, top: 0 }),
})

// main 文件中安装至 app 实例
import { router } from '@/router'

app.use(router)

export function createRouter(options: RouterOptions): Router {
  /*...*/
}

export interface RouterOptions extends PathParserOptions {
  // 定义路由导航方式，分为 hash 模式和 history 模式
  history: RouterHistory
  // 初始化路由列表
  routes: Readonly<RouteRecordRaw[]>
  // 路由跳转后滚动事件
  scrollBehavior?: RouterScrollBehavior
  // 解析和序列化路由参数，常用于路由参数加密
  parseQuery?: typeof originalParseQuery
  stringifyQuery?: typeof originalStringifyQuery
  // 定义 router-link 组件的链接被点击后，默认在链接上添加的 class 名称
  linkActiveClass?: string
  linkExactActiveClass?: string
}

export interface Router {
  // 当前路由
  readonly currentRoute: Ref<RouteLocationNormalizedLoaded>
  // 路由配置项，即 createRouter 传入参数
  readonly options: RouterOptions
  // 是否允许监听 history 事件，通常用于微前端
  listening: boolean

  // 路由的 crud
  addRoute(parentName: RouteRecordName, route: RouteRecordRaw): () => void
  addRoute(route: RouteRecordRaw): () => void
  removeRoute(name: RouteRecordName): void
  hasRoute(name: RouteRecordName): boolean
  getRoutes(): RouteRecord[]

  // 返回路由地址的标准化版本
  resolve(
    to: RouteLocationRaw,
    currentLocation?: RouteLocationNormalizedLoaded
  ): RouteLocation & { href: string }

  // 路由 push 跳转，history 栈会增加跳转路由
  push(to: RouteLocationRaw): Promise<NavigationFailure | void | undefined>

  // 路由 replace 跳转，更换 history 栈顶元素
  replace(to: RouteLocationRaw): Promise<NavigationFailure | void | undefined>

  // 路由后退、前进、跳转
  back(): ReturnType<Router['go']>
  forward(): ReturnType<Router['go']>
  go(delta: number): void

  // 路由守卫三个方法
  beforeEach(guard: NavigationGuardWithThis<undefined>): () => void
  beforeResolve(guard: NavigationGuardWithThis<undefined>): () => void
  afterEach(guard: NavigationHookAfter): () => void
  // 路由错误处理
  onError(handler: _ErrorHandler): () => void
  // 是否完成初始化导航
  isReady(): Promise<void>
  // vue 实例注册 router 的方法
  install(app: App): void
}

export function createRouter(options: RouterOptions): Router {
  // 解析路由配置，创建路由规则，处理路由匹配
  const matcher = createRouterMatcher(options.routes, options)
  // 路由参数处理
  const parseQuery = options.parseQuery || originalParseQuery
  const stringifyQuery = options.stringifyQuery || originalStringifyQuery
  // 定义路由历史记录处理方式，分为 hash 和 history
  const routerHistory = options.history

  // 定义路由守卫
  const beforeGuards = useCallbacks<NavigationGuardWithThis<undefined>>()
  const beforeResolveGuards = useCallbacks<NavigationGuardWithThis<undefined>>()
  const afterGuards = useCallbacks<NavigationHookAfter>()

  // 定义当前路由
  const currentRoute = shallowRef<RouteLocationNormalizedLoaded>(START_LOCATION_NORMALIZED)
  // 暂存正在进行的导航操作，用于地址变化时判断导航是否完成
  let pendingLocation: RouteLocation = START_LOCATION_NORMALIZED

  // 路由参数规范化
  const normalizeParams = applyToParams.bind(null, (paramValue) => '' + paramValue)
  const encodeParams = applyToParams.bind(null, encodeParam)
  const decodeParams: (params: RouteParams | undefined) => RouteParams = applyToParams.bind(
    null,
    decode
  )

  let started: boolean | undefined
  const installedApps = new Set<App>()

  const router: Router = {
    /* router 实例属性 */
    install,
  }

  return router
}

export function createRouterMatcher(
  routes: Readonly<RouteRecordRaw[]>,
  globalOptions: PathParserOptions
): RouterMatcher {
  // 定义 matchers 数组，存储所有路由匹配规则
  const matchers: RouteRecordMatcher[] = []
  // 定义 matcher Map，通过 路由名称 更快的定位到匹配规则
  const matcherMap = new Map<RouteRecordName, RouteRecordMatcher>()
  // 合并选项参数
  globalOptions = mergeOptions(
    { strict: false, end: true, sensitive: false } as PathParserOptions,
    globalOptions
  )

  // 通过 路由名称获取对应 matchers
  function getRecordMatcher(name: RouteRecordName) {}

  // 添加路由
  function addRoute(
    record: RouteRecordRaw,
    parent?: RouteRecordMatcher,
    originalRecord?: RouteRecordMatcher
  ) {}

  function removeRoute(matcherRef: RouteRecordName | RouteRecordMatcher) {}

  // 获取 matchers 数组
  function getRoutes() {}

  // 新增 matcher
  function insertMatcher(matcher: RouteRecordMatcher) {}

  // 获得路由的标准化版本
  function resolve(
    location: Readonly<MatcherLocationRaw>,
    currentLocation: Readonly<MatcherLocation>
  ): MatcherLocation {}

  // 遍历初始化路由，对每一个路由使用 addRoute 方法处理
  routes.forEach((route) => addRoute(route))

  return { addRoute, resolve, removeRoute, getRoutes, getRecordMatcher }
}

function removeRoute(matcherRef: RouteRecordName | RouteRecordMatcher) {
  if (isRouteName(matcherRef)) {
    const matcher = matcherMap.get(matcherRef)
    if (matcher) {
      matcherMap.delete(matcherRef)
      matchers.splice(matchers.indexOf(matcher), 1)
      matcher.children.forEach(removeRoute)
      matcher.alias.forEach(removeRoute)
    }
  } else {
    const index = matchers.indexOf(matcherRef)
    if (index > -1) {
      matchers.splice(index, 1)
      if (matcherRef.record.name) matcherMap.delete(matcherRef.record.name)
      matcherRef.children.forEach(removeRoute)
      matcherRef.alias.forEach(removeRoute)
    }
  }
}

import { parseQuery as originalParseQuery, stringifyQuery as originalStringifyQuery } from './query'

const parseQuery = options.parseQuery || originalParseQuery
const stringifyQuery = options.stringifyQuery || originalStringifyQuery

const router: Router = {
  install(app: App) {
    const router = this
    // 向 vue 中注册两个路由内置组件
    app.component('RouterLink', RouterLink)
    app.component('RouterView', RouterView)

    // 定义 $router 属性，可以直接通过 this.$router 访问 router 属性
    app.config.globalProperties.$router = router
    Object.defineProperty(app.config.globalProperties, '$route', {
      enumerable: true,
      get: () => unref(currentRoute),
    })

    // 初始化 router 时设置 started 属性为 true，避免 router 实例注册到多个 vue 实例时重复加载
    if (isBrowser && !started && currentRoute.value === START_LOCATION_NORMALIZED) {
      started = true
    }

    // 设置初始化路由属性并赋值
    const reactiveRoute = {} as {
      [k in keyof RouteLocationNormalizedLoaded]: ComputedRef<RouteLocationNormalizedLoaded[k]>
    }
    for (const key in START_LOCATION_NORMALIZED) {
      reactiveRoute[key] = computed(() => currentRoute.value[key])
    }

    // 向 vue 实例中注入 router 等属性，便于全局使用
    app.provide(routerKey, router)
    app.provide(routeLocationKey, reactive(reactiveRoute))
    app.provide(routerViewLocationKey, currentRoute)

    // 定义 vue 实例卸载的 unmount 方法，重置相关属性，注意 started 设置为 false
    const unmountApp = app.unmount
    installedApps.add(app)
    app.unmount = function () {
      installedApps.delete(app)
      // the router is not attached to an app anymore
      if (installedApps.size < 1) {
        // invalidate the current navigation
        pendingLocation = START_LOCATION_NORMALIZED
        removeHistoryListener && removeHistoryListener()
        removeHistoryListener = null
        currentRoute.value = START_LOCATION_NORMALIZED
        started = false
        ready = false
      }
      unmountApp()
    }
  },
}