如何自主设计实现一个 Vue 路由系统？

1. 路由表定义

路由表是一个数组，包含每个路由的路径和对应的组件信息，还可以包括一些额外的配置，如嵌套路由、重定向、别名等。

const routes = [
  {
    path: '/',
    component: HomeComponent,
    children: [
      { path: 'profile', component: ProfileComponent }
    ]
  },
  { path: '/about', component: AboutComponent },
  { path: '/contact', component: ContactComponent },
  { path: '/user/:id', component: UserComponent }
];

2. 路由解析和匹配

我们需要一个解析器来匹配当前的 URL 并找到对应的路由。可以使用正则表达式来处理动态路由参数。

function matchRoute(path, routes) {
  for (let route of routes) {
    const regex = new RegExp(`^${route.path.replace(/:\w+/g, '(\\w+)')}$`);
    const match = path.match(regex);
    if (match) {
      return { ...route, params: extractParams(route.path, match) };
    }
  }
  return null;
}

function extractParams(routePath, match) {
  const keys = routePath.match(/:\w+/g);
  const params = {};
  if (keys) {
    keys.forEach((key, index) => {
      params[key.replace(':', '')] = match[index + 1];
    });
  }
  return params;
}

3. 路由组件渲染

在 Vue 应用中，我们使用一个根组件来动态渲染当前匹配的组件。

const App = {
  data() {
    return {
      currentRoute: window.location.pathname,
      currentComponent: null
    };
  },
  created() {
    this.updateRoute();
    window.addEventListener('popstate', this.updateRoute);
  },
  methods: {
    updateRoute() {
      const match = matchRoute(this.currentRoute, routes);
      if (match) {
        this.currentComponent = match.component;
      } else {
        this.currentComponent = NotFoundComponent;
      }
    },
    navigate(path) {
      history.pushState(null, null, path);
      this.currentRoute = path;
      this.updateRoute();
    }
  },
  render() {
    return Vue.h(this.currentComponent);
  }
};

4. 导航守卫

导航守卫可以在路由切换之前或之后执行一些逻辑，如权限检查、数据获取等。可以在路由对象中定义 beforeEnter 钩子。

const routes = [
  {
    path: '/',
    component: HomeComponent,
    beforeEnter(to, from, next) {
      // 执行一些逻辑
      next();
    }
  },
  { path: '/about', component: AboutComponent }
];

function updateRoute() {
  const match = matchRoute(window.location.pathname, routes);
  if (match && match.beforeEnter) {
    match.beforeEnter(match, currentRoute, () => {
      currentComponent = match.component;
    });
  } else if (match) {
    currentComponent = match.component;
  } else {
    currentComponent = NotFoundComponent;
  }
}

5. 嵌套路由

嵌套路由允许在一个组件内部定义子路由。可以使用递归来渲染子路由。

const HomeComponent = {
  template: '<div>Home <router-view></router-view></div>',
  components: {
    'router-view': {
      render() {
        const currentRoute = window.location.pathname.replace('/profile', '');
        const match = matchRoute(currentRoute, routes[0].children);
        return Vue.h(match ? match.component : NotFoundComponent);
      }
    }
  }
};

6. 其他特性

命名视图：允许在同一路由中渲染多个视图。

动态路由：通过 URL 参数传递数据。

重定向和别名：支持重定向路径和别名路径。

7. 完整示例

const HomeComponent = {
  template: '<div>Home <router-view></router-view></div>',
};

const ProfileComponent = {
  template: '<div>Profile</div>',
};

const AboutComponent = {
  template: '<div>About</div>',
};

const ContactComponent = {
  template: '<div>Contact</div>',
};

const UserComponent = {
  props: ['id'],
  template: '<div>User {{ id }}</div>',
};

const NotFoundComponent = {
  template: '<div>404 Not Found</div>',
};

const routes = [
  {
    path: '/',
    component: HomeComponent,
    children: [
      { path: 'profile', component: ProfileComponent }
    ]
  },
  { path: '/about', component: AboutComponent },
  { path: '/contact', component: ContactComponent },
  { path: '/user/:id', component: UserComponent }
];

function matchRoute(path, routes) {
  for (let route of routes) {
    const regex = new RegExp(`^${route.path.replace(/:\w+/g, '(\\w+)')}$`);
    const match = path.match(regex);
    if (match) {
      return { ...route, params: extractParams(route.path, match) };
    }
  }
  return null;
}

function extractParams(routePath, match) {
  const keys = routePath.match(/:\w+/g);
  const params = {};
  if (keys) {
    keys.forEach((key, index) => {
      params[key.replace(':', '')] = match[index + 1];
    });
  }
  return params;
}

const App = {
  data() {
    return {
      currentRoute: window.location.pathname,
      currentComponent: null
    };
  },
  created() {
    this.updateRoute();
    window.addEventListener('popstate', this.updateRoute);
  },
  methods: {
    updateRoute() {
      const match = matchRoute(this.currentRoute, routes);
      if (match) {
        this.currentComponent = match.component;
      } else {
        this.currentComponent = NotFoundComponent;
      }
    },
    navigate(path) {
      history.pushState(null, null, path);
      this.currentRoute = path;
      this.updateRoute();
    }
  },
  render() {
    return Vue.h(this.currentComponent);
  }
};

const app = Vue.createApp(App);
app.mount('#app');

总结

这个示例展示了如何设计和实现一个基本的 Vue 路由系统。我们定义了路由表，通过正则表达式解析 URL，匹配路由并渲染相应的组件。系统还支持嵌套路由、动态路由参数、导航守卫等功能。尽管这是一个简化的实现，但它展示了 Vue Router 的基本原理。实际应用中，完整的路由系统可能会更复杂，处理更多的场景和优化。