vue-router源码探究

路由管理

• 前端应用中重要的机制-页面根据 URL 的变化进行切换
• Uniform Resource Locator
• 页面+状态（定位）
• 根据状态渲染不同的组件

核心逻辑简单实现

// 基于hash实现
const MyRouter = ({ children }) => {
  const routes = _.keyBy(
    children.map((c) => c.props),
    "path",
  );
  const [hash] = useHash();
  const Page = routes[hash.replace("#", "")]?.component;
  return Page ? <Page /> : "Not found.";
};


const Route = () => null;

<div className="sample-pages">
  <div className="sider">
    <a href="#page1">Page 1</a>
    <a href="#page2">Page 2</a>
    <a href="#page3">Page 3</a>
    <a href="#page4">Page 4</a>
  </div>
  <div className="exp-15-page-container">
    <MyRouter>
      <Route path="page1" component={Page1} />
      <Route path="page2" component={Page2} />
      <Route path="page3" component={Page3} />
      <Route path="page4" component={Page4} />
    </MyRouter>
  </div>
</>

源码探究

具体配置执行了什么

• 拉下代码看下
• https://github.com/vuejs/vue-router.git

base

base
类型: string

默认值: "/"

应用的基路径。例如，如果整个单页应用服务在 /app/ 下，然后 base 就应该设为 "/app/"。

//   options: RouterOptions | options.base
export interface RouterOptions {
  routes?: RouteConfig[]
  mode?: RouterMode
  fallback?: boolean
  base?: string
  linkActiveClass?: string
  linkExactActiveClass?: string
  parseQuery?: (query: string) => Object
  stringifyQuery?: (query: Object) => string
  scrollBehavior?: (
    to: Route,
    from: Route,
    savedPosition: Position | void
  ) => PositionResult | Promise<PositionResult> | undefined | null
}
export default class VueRouter {
  static install: () => void
  static version: string
  static isNavigationFailure: Function
  static NavigationFailureType: any
  static START_LOCATION: Route

  app: any
  apps: Array<any>
  ready: boolean
  readyCbs: Array<Function>
  options: RouterOptions
  mode: string
  history: HashHistory | HTML5History | AbstractHistory
  matcher: Matcher
  fallback: boolean
  beforeHooks: Array<?NavigationGuard>
  resolveHooks: Array<?NavigationGuard>
  afterHooks: Array<?AfterNavigationHook>

  constructor (options: RouterOptions = {}) {
    this.app = null
    this.apps = []
    this.options = options
    this.beforeHooks = []
    this.resolveHooks = []
    this.afterHooks = []
    this.matcher = createMatcher(options.routes || [], this)

    let mode = options.mode || 'hash'
    this.fallback =
      mode === 'history' && !supportsPushState && options.fallback !== false
    if (this.fallback) {
      mode = 'hash'
    }
    if (!inBrowser) {
      mode = 'abstract'
    }
    this.mode = mode

    switch (mode) {
      case 'history':
        this.history = new HTML5History(this, options.base)
        break
      case 'hash':
        this.history = new HashHistory(this, options.base, this.fallback)
        break
      case 'abstract':
        this.history = new AbstractHistory(this, options.base)
        break
      default:
        if (process.env.NODE_ENV !== 'production') {
          assert(false, `invalid mode: ${mode}`)
        }
    }
  }

  match (raw: RawLocation, current?: Route, redirectedFrom?: Location): Route {
    return this.matcher.match(raw, current, redirectedFrom)
  }

  get currentRoute (): ?Route {
    return this.history && this.history.current
  }

  init (app: any /* Vue component instance */) {
    process.env.NODE_ENV !== 'production' &&
      assert(
        install.installed,
        `not installed. Make sure to call \`Vue.use(VueRouter)\` ` +
          `before creating root instance.`
      )

    this.apps.push(app)

    // set up app destroyed handler
    // https://github.com/vuejs/vue-router/issues/2639
    app.$once('hook:destroyed', () => {
      // clean out app from this.apps array once destroyed
      const index = this.apps.indexOf(app)
      if (index > -1) this.apps.splice(index, 1)
      // ensure we still have a main app or null if no apps
      // we do not release the router so it can be reused
      if (this.app === app) this.app = this.apps[0] || null

      if (!this.app) this.history.teardown()
    })

    // main app previously initialized
    // return as we don't need to set up new history listener
    if (this.app) {
      return
    }

    this.app = app

    const history = this.history

    if (history instanceof HTML5History || history instanceof HashHistory) {
      const handleInitialScroll = routeOrError => {
        const from = history.current
        const expectScroll = this.options.scrollBehavior
        const supportsScroll = supportsPushState && expectScroll

        if (supportsScroll && 'fullPath' in routeOrError) {
          handleScroll(this, routeOrError, from, false)
        }
      }
      const setupListeners = routeOrError => {
        history.setupListeners()
        handleInitialScroll(routeOrError)
      }
      history.transitionTo(
        history.getCurrentLocation(),
        setupListeners,
        setupListeners
      )
    }

    history.listen(route => {
      this.apps.forEach(app => {
        app._route = route
      })
    })
  }

  beforeEach (fn: Function): Function {
    return registerHook(this.beforeHooks, fn)
  }

  beforeResolve (fn: Function): Function {
    return registerHook(this.resolveHooks, fn)
  }

  afterEach (fn: Function): Function {
    return registerHook(this.afterHooks, fn)
  }

  onReady (cb: Function, errorCb?: Function) {
    this.history.onReady(cb, errorCb)
  }

  onError (errorCb: Function) {
    this.history.onError(errorCb)
  }

  push (location: RawLocation, onComplete?: Function, onAbort?: Function) {
    // $flow-disable-line
    if (!onComplete && !onAbort && typeof Promise !== 'undefined') {
      return new Promise((resolve, reject) => {
        this.history.push(location, resolve, reject)
      })
    } else {
      this.history.push(location, onComplete, onAbort)
    }
  }

  replace (location: RawLocation, onComplete?: Function, onAbort?: Function) {
    // $flow-disable-line
    if (!onComplete && !onAbort && typeof Promise !== 'undefined') {
      return new Promise((resolve, reject) => {
        this.history.replace(location, resolve, reject)
      })
    } else {
      this.history.replace(location, onComplete, onAbort)
    }
  }

  go (n: number) {
    this.history.go(n)
  }

  back () {
    this.go(-1)
  }

  forward () {
    this.go(1)
  }

  getMatchedComponents (to?: RawLocation | Route): Array<any> {
    const route: any = to
      ? to.matched
        ? to
        : this.resolve(to).route
      : this.currentRoute
    if (!route) {
      return []
    }
    return [].concat.apply(
      [],
      route.matched.map(m => {
        return Object.keys(m.components).map(key => {
          return m.components[key]
        })
      })
    )
  }

  resolve (
    to: RawLocation,
    current?: Route,
    append?: boolean
  ): {
    location: Location,
    route: Route,
    href: string,
    // for backwards compat
    normalizedTo: Location,
    resolved: Route
  } {
    current = current || this.history.current
    const location = normalizeLocation(to, current, append, this)
    const route = this.match(location, current)
    const fullPath = route.redirectedFrom || route.fullPath
    const base = this.history.base
    const href = createHref(base, fullPath, this.mode)
    return {
      location,
      route,
      href,
      // for backwards compat
      normalizedTo: location,
      resolved: route
    }
  }

  getRoutes () {
    return this.matcher.getRoutes()
  }

  addRoute (parentOrRoute: string | RouteConfig, route?: RouteConfig) {
    this.matcher.addRoute(parentOrRoute, route)
    if (this.history.current !== START) {
      this.history.transitionTo(this.history.getCurrentLocation())
    }
  }

  addRoutes (routes: Array<RouteConfig>) {
    if (process.env.NODE_ENV !== 'production') {
      warn(false, 'router.addRoutes() is deprecated and has been removed in Vue Router 4. Use router.addRoute() instead.')
    }
    this.matcher.addRoutes(routes)
    if (this.history.current !== START) {
      this.history.transitionTo(this.history.getCurrentLocation())
    }
  }
}

pushState

function pushState (url, replace) {
  saveScrollPosition();
  // try...catch the pushState call to get around Safari
  // DOM Exception 18 where it limits to 100 pushState calls
  var history = window.history;
  try {
    if (replace) {
      history.replaceState({ key: _key }, '', url);
    } else {
      _key = genKey();
      history.pushState({ key: _key }, '', url);
    }
  } catch (e) {
    window.location[replace ? 'replace' : 'assign'](url);
  }
}

function replaceState (url) {
  pushState(url, true);
}

其他

react router

• https://reactrouter.com/web/guides/quick-start
• 支持多端（web browser, react native）
• react-router-dom
• BrowserRouter | Link | Route | Switch

  The react-router package is the heart of React Router and provides all the core functionality for both react-router-dom and react-router-native.
  
  If you're using React Router, you should never import anything directly from the react-router package, but you should have everything you need in either react-router-dom or react-router-native. Both of those packages re-export everything from react-router.
  
  If you'd like to extend React Router and you know what you're doing, you should add react-router as a peer dependency, not a regular dependency in your package.
  
  react-router包是React Router的核心，为react-router-dom和react-router-native提供所有核心功能。
  
  如果你正在使用 React Router，你不应该直接从 react-router 包中导入任何东西，但你应该在 react-router-dom 或 react-router-native 中拥有你需要的一切。这两个包都从 react-router 重新导出了所有东西。
  
  如果你想扩展 React Router，并且你知道你在做什么，你应该把 react-router 作为peer dependency，而不是在你的包中作为regular dependency。

• react-router-config

  import { renderRoutes } from 'react-router-config';//renderRoutes 读取路由配置转化为 Route 标签
  renderRoutes 这个方法只渲染一层路由

  应用场景

嵌套路由

URL 中保存页面状态

权限控制

window.history

• https://html.spec.whatwg.org/multipage/history.html
• browsing session

  A browsing session is …. See whatwg/html issue #4782 and whatwg/html issue #5350 for defining browsing session. It is roughly analogous to a top-level browsing context except that it cannot be replaced due to a `Cross-Origin-Opener-Policy` header or navigation.
  
  A top-level browsing context has an associated browsing session which is a browsing session.
  
  The browsing session of an environment settings object environment is the result of running these steps:
  
  Assert: environment has a responsible document.
  
  Return environment's responsible document's browsing context's top-level browsing context's browsing session.

location.pathname

popstate

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