react-router-dom 5.X

安装

npm install --save react-router-dom

使用

导入

import { BrowserRouter as Router, Route, Link } from "react-router-dom";
上述import是es6语法，其中as是取别名用的

简单实例

import React from 'react';
import { BrowserRouter as Router, Route, Link } from "react-router-dom";
import Home from './components/Home'
import News from './components/News'
import Music from './components/Music'

function App() {
  return (
    <Router>
      <Route exact path="/" component={Home} />{/* exact准确匹配 */}
      <Route path="/news" component={News} />
      <Route path="/music" component={Music} />
    </Router>
  );
}

export default App;

注意，每个路由必须被外层的Router包裹
exact的存在是严格匹配，去掉的话，访问/news实际会渲染Home

Link的使用

类似vue的vue-router,实际每个Link默认被渲染为a标签

<Link to='/' > 首页</Link>
<Link to='/news'>新闻</Link>
<Link to='/music'>音乐</Link>

react-router-dom 官方示例解读

BasicExample–基础实例

这是一个最基础的路由示例，根据不同的url渲染不同的组件。值得注意的是，对于Route组件而言，支持的渲染组件方式不唯一。单标签的时候可以使用component属性，render属性，或者children属性挂载要渲染的组件。双标签的时候包裹要渲染的组件，也就是children…

import React from 'react'
import {
    BrowserRouter as Router,
    Switch,
    Route,
    Link
} from "react-router-dom";

const Home = () => <h2>Home</h2>
const About = () => <h2>About</h2>
const Dashboard = () => <h2>Dashboard</h2>
const News = () => <h2>News</h2>
const Games = () => <h2>Games</h2>

export default function () {
    return (
        <Router>
            <div>
                <ul>
                    <li> <Link to="/">Home</Link> </li>
                    <li>  <Link to="/about">About</Link>  </li>
                    <li>  <Link to="/dashboard">Dashboard</Link> </li>
                    <li>  <Link to="/news">News</Link> </li>
                    <li>  <Link to="/games">Games</Link> </li>
                </ul>
                <hr />
                <Switch>
                    <Route exact path="/"> <Home /></Route>
                    <Route path="/about" component={About} />
                    <Route path="/dashboard" children={<Dashboard />} />
                    <Route path="/news" render={()=><News />} />
                    <Route path="/games" component={()=><Games/>} />
                </Switch>
            </div>
        </Router>
    );
}

UrlParams–动态路由

 该示例演示了动态路由是如何匹配的，以及如何获取匹配到的参数值。和很多框架匹配规则一致，都是:param.在获取参数的时候，可以用hooks形式 ，也可以用原始的props.match.params.xxx

import React from "react";
import {
    BrowserRouter as Router,
    Switch,
    Route,
    Link,
    useParams
} from "react-router-dom";


export default function () {
    return (
        <Router>
            <div>
                <h2>Accounts</h2>
                <ul>
                    <li>
                        <Link to="/netflix/1">Netflix</Link>
                    </li>
                    <li>
                        <Link to="/zillow-group/2">Zillow Group</Link>
                    </li>
                    <li>
                        <Link to="/yahoo/3">Yahoo</Link>
                    </li>
                    <li>
                        <Link to="/modus-create/4">Modus Create</Link>
                    </li>
                </ul>
                <Switch>
                    <Route path="/:page/:num" component={Child} />
                </Switch>
            </div>
        </Router>
    );
}

function Child(props) {
    let { page} = useParams();
    let num=props.match.params.num;
    return (
        <div>
            <h3>
                当前页: {page}--数字:{num}
            </h3>
        </div>
    );
}

Nesting–嵌套路由

 嵌套路由适用于有明显层级划分的情况，以官方示例来看，主层级分为home和topics,topics又划分出三个子主题，这就涉及到了嵌套路由。子路由的url都是在父级路由基础上拼接出来的。像这样 /topics /topics/rendering。值得注意的是，这个案例里用到了一个新的hooks,useRouteMatch,这就相当于原始的props.match.此外，这个示例里对useRouteMatch(）解构了path和url，如果你打印一下，你会发现它们的值是一样的，也许就像原文解释那样，一个用来获取父路径，一个用于Link组件的跳转，更规范？

import React from "react";
import {
    BrowserRouter as Router,
    Switch,
    Route,
    Link,
    useParams,
    useRouteMatch
} from "react-router-dom";

const Home = () => <h2>Home</h2>

const Topic = () => {
    let { topicId } = useParams();
    return <h3>{topicId}</h3>
}

const Topics = () => {

    let { path, url } = useRouteMatch();
    return (
        <div>
            <h2>Topics</h2>
            <ul>
                <li><Link to={`${url}/rendering`}>Rendering with React</Link></li>
                <li><Link to={`${url}/components`}>Components</Link></li>
                <li><Link to={`${url}/props-v-state`}>Props v. State</Link></li>
            </ul>
            <Switch>
                <Route exact path={path}> <h3>Please select a topic.</h3></Route>
                <Route path={`${path}/:topicId`} component={Topic} />
            </Switch>
        </div>
    );
}

export default function () {
    return (
        <Router>
            <div>
                <ul>
                    <li><Link to="/">Home</Link></li>
                    <li><Link to="/topics">Topics</Link></li>
                </ul>
                <hr />
                <Switch>
                    <Route exact path="/" component={Home} />
                    <Route path="/topics" component={Topics} />
                </Switch>
            </div>
        </Router>
    );
}

AuthRoute–路由鉴权

这个demo.核心是通过高阶组件+状态控制实现路由鉴权。在实际开发中，有些页面必须登录才可以访问，甚至不同身份的人看到的页面也是不一样的。public页面都可以访问，protected页面必须登录才可以访问。登录状态这里使用一个变量isLogin控制.Redirect 组件用于身份验证不通过时重定向处理，useHistory 钩子函数可获取历史记录接口，控制页面跳转。PrivateRoute 是一个高阶组件，对基础的Route进行了进一步封装，注意...rest，在这里相当于将高阶组件获取的path属性传递给Route

import React from "react";
import {
  BrowserRouter as Router,
  Switch,
  Route,
  Link,
  Redirect,
  useHistory,
} from "react-router-dom";

let isLogin = false;

const LoginBtn = () =>   <button onClick={()=>{isLogin = true}}>登录</button>

const LoginOutBtn = () => {
  let history=useHistory();
  return <button onClick={()=>{isLogin = false;history.push("/login")}}>退出登录</button>
}

const Login = () => <LoginBtn/>

const Condition = ({ children }) => isLogin ? children : <Redirect to="/login" />


const PrivateRoute = ({ children, ...rest }) => {
  return (
    <Route   {...rest} render={() => <Condition children={children} />} />
  );
}

export default function () {
  return (
    <Router>
      <p><Link to={"/public"} >public</Link></p>
      <p><Link to={"/protected"}>protected</Link></p>
      <Switch>
        <Route exact path="/" render={() => <h3>home</h3>} />
        <Route path="/public" render={() => <h3>public</h3>} />
        <Route path="/login" component={Login} />
        <PrivateRoute path="/protected">
          <h2>已经登录 可查看-protected</h2>
          <LoginOutBtn/>
        </PrivateRoute>
      </Switch>
    </Router>
  )
}

CustomLink–自定义路由 

自定义路由本质是在Route组件的基础上加入了一些定制化处理，相当于包裹了一层。为了更好理解，这里对官方示例做了个微调，强匹配属性exact直接写入而不是传参形式体现。useRouteMatch可以根据path返回一个匹配结果对象,exact表示强匹配
，借助于Route组件,useRouteMatch可以空调用,像这样useRouteMatch().反之,需要传参。可嵌套路由，对比查看。

import React from "react";
import {
    BrowserRouter as Router,
    Switch,
    Route,
    Link,
    useRouteMatch
} from "react-router-dom";


const Home = () => <h2>Home</h2>
const About = () => <h2>About</h2>

export default function () {
    return (
        <Router>
            <div>
                <MyLink to="/" label="Home" />
                <MyLink to="/about" label="About" />
                <hr />
                <Switch>
                    <Route exact path="/" component={Home} />
                    <Route path="/about" component={About} />
                </Switch>
            </div>
        </Router>
    );
}

function MyLink({ label, to }) {
    let match = useRouteMatch({
        path: to,
        exact: true
    })
    // 这里返回的match对象仅用于样式控制

    return (
        <div className={match ? "active" : ""}>
            {match && "> "}
            <Link to={to}>{label}</Link>
        </div>
    );
}

PreventingTransitions–阻止过渡

正常情况下，在用户在表单中填写了一些信息但是没提交的情况下，点击其他页面跳转链接，等再返回的时候，表单数据会丢失。这个例子就是提供一种阻断方式，在进行页面跳转的时候给用户一个提示，确认后会跳转，避免因为误操作导致的表单数据丢失。提示这里使用的是Prompt组件，when属性为一个布尔值，true弹出提示框，message为具体的提示信息。Prompt也可以写在form之外，保证在要渲染的组件里即可。这种场景，通常用于长表单输入，比如注册。关于Prompt，还有个好用的点，下边单独介绍。

import React, { useState } from "react";
import {
  BrowserRouter as Router,
  Switch,
  Route,
  Link,
  Prompt
} from "react-router-dom";

// Sometimes you want to prevent the user from
// navigating away from a page. The most common
// use case is when they have entered some data
// into a form but haven't submitted it yet, and
// you don't want them to lose it.

export default function PreventingTransitionsExample() {
  return (
    <Router>
      <ul>
        <li>
          <Link to="/">Form</Link>
        </li>
        <li>
          <Link to="/one">One</Link>
        </li>
        <li>
          <Link to="/two">Two</Link>
        </li>
      </ul>

      <Switch>
        <Route path="/" exact children={<BlockingForm />} />
        <Route path="/one" children={<h3>One</h3>} />
        <Route path="/two" children={<h3>Two</h3>} />
      </Switch>
    </Router>
  );
}

function BlockingForm() {
  let [isBlocking, setIsBlocking] = useState(false);

  return (
    <form
      onSubmit={event => {
        event.preventDefault();
        event.target.reset();
        setIsBlocking(false);
      }}
    >
      <Prompt
        when={isBlocking}
        message={location =>
          `Are you sure you want to go to ${location.pathname}`
        }
      />

      <p>
        Blocking?{" "}
        {isBlocking ? "Yes, click a link or the back button" : "Nope"}
      </p>

      <p>
        <input
          size="50"
          placeholder="type something to block transitions"
          onChange={event => {
            setIsBlocking(event.target.value.length > 0);
          }}
        />
      </p>

      <p>
        <button>Submit to stop blocking</button>
      </p>
    </form>
  );
}

Prompt

• message属性还可以接收一个函数，该函数可以获取到下一个位置（location），返回true不提示，反之，弹出提示

<Prompt message={location =>
          location.pathname.startsWith("/one")
            ? true
            : `Are you sure you want to go to ${location.pathname}?`
        }
      />

NO Match–404

 该示例演示的是对404的处理，用于捕获所有未匹配的项，通常放置于Switch的最后一项Route里，匹配规则为*。当然，也许你还想将所有的未捕获页面都跳转到/error，这个需要使用重定向，后边会介绍

import React from "react";
import {
  BrowserRouter as Router,
  Route,
  Link,
  Switch,
  Redirect,
  useLocation
} from "react-router-dom";



export default function NoMatchExample() {
  return (
    <Router>
      <div>
        <ul>
          <li>
            <Link to="/">Home</Link>
          </li>
          <li>
            <Link to="/old-match">Old Match, to be redirected</Link>
          </li>
          <li>
            <Link to="/will-match">Will Match</Link>
          </li>
          <li>
            <Link to="/will-not-match">Will Not Match</Link>
          </li>
          <li>
            <Link to="/also/will/not/match">Also Will Not Match</Link>
          </li>
        </ul>

        <Switch>
          <Route exact path="/">
            <Home />
          </Route>
          <Route path="/old-match">
            <Redirect to="/will-match" />
          </Route>
          <Route path="/will-match">
            <WillMatch />
          </Route>
        <Route path="*" >
            <NoMatch />
          </Route>
         
        </Switch>
      </div>
    </Router>
  );
}

function Home() {
  return <h3>Home</h3>;
}

function WillMatch() {
  return <h3>Matched!</h3>;
}

function NoMatch() {
  let location = useLocation();

  return (
    <div>
      <h3>
        No match for <code>{location.pathname}</code>
      </h3>
    </div>
  );
}

统一处理404

 <Switch>
  <Route path="/one" component={One}/>
  <Route path="/two" component={Two}/>
  <Route path="/error" component={Error}/>
  <Redirect from="/*" to="/error" />
</Switch>

Sidebar 侧边栏

侧边栏这个案例很常见，官方示例里边介绍的除了基础侧边栏，还扩展了一种多处渲染的方式。即当路由匹配到当前url时，可以在应用给程序内任何你想渲染的地方去分别渲染sideber和main，注意下边的map遍历，只有children属性那里有差异

import React from "react";

import {render} from "react-dom";
import {
  BrowserRouter as Router,
  Switch,
  Route,
  Link
} from "react-router-dom";


const routes = [
  {
    path: "/",
    exact: true,
    sidebar: () => <div>home!</div>,
    main: () => <h2>Home</h2>
  },
  {
    path: "/bubblegum",
    sidebar: () => <div>bubblegum!</div>,
    main: () => <h2>Bubblegum</h2>
  },
  {
    path: "/shoelaces",
    sidebar: () => <div>shoelaces!</div>,
    main: () => <h2>Shoelaces</h2>
  }
];

export default function SidebarExample() {
  return (
    <Router>
      <div style={{ display: "flex" }}>
        <div
          style={{
            padding: "10px",
             "40%",
            background: "#f0f0f0"
          }}
        >
          <ul style={{ listStyleType: "none", padding: 0 }}>
            <li>
              <Link to="/">Home</Link>
            </li>
            <li>
              <Link to="/bubblegum">Bubblegum</Link>
            </li>
            <li>
              <Link to="/shoelaces">Shoelaces</Link>
            </li>
          </ul>

          <Switch>
            {routes.map((route, index) => (
             
              <Route
                key={index}
                path={route.path}
                exact={route.exact}
                
                children={<route.sidebar />}
              />
            ))}
          </Switch>
        </div>

        <div style={{ flex: 1, padding: "10px" }}>
          <Switch>
            {routes.map((route, index) => (
              <Route
                key={index}
                path={route.path}
                exact={route.exact}
                
                children={<route.main />}
              />
            ))}
          </Switch>
        </div>
      </div>
    </Router>
  );
}

render(<SidebarExample/>,document.getElementById("root"))

• 结合效果图来看，侧边栏底部和右侧，都进行了渲染，即多处渲染。注意，这两次其实除了渲染的组件不同，其他都一样

config 路由配置

 有时候，也许你希望将路由集中配置，比如放在一个数组里，每个路由对象包含path和component。涉及嵌套的，就再来一个数组，存放子路由对象。

import React from "react";
import { render } from 'react-dom'
import {
  BrowserRouter as Router,
  Switch,
  Route,
  Link
} from "react-router-dom";


const Sandwiches = () => <h2>Sandwiches</h2>
const Bus = () => <h2>Bus</h2>
const Cart = () => <h2>Cart</h2>

const routes = [
  {
    path: "/sandwiches",
    component: Sandwiches
  },
  {
    path: "/tacos",
    component: Tacos,
    routes: [
      {
        path: "/tacos/bus",
        component: Bus
      },
      {
        path: "/tacos/cart",
        component: Cart
      }
    ]
  }
];

export default function App() {
  return (
    <Router>
      <div>
        <ul>
          <li>
            <Link to="/tacos">Tacos</Link>
          </li>
          <li>
            <Link to="/sandwiches">Sandwiches</Link>
          </li>
        </ul>


        <Switch>
          {routes.map((route, i) => (
            <RouteWithSubRoutes key={i} {...route} />
          ))}
        </Switch>
      </div>
    </Router>
  );
}

function RouteWithSubRoutes(route) {

  return (
    <Route
      path={route.path}
      render={(props) => {
        return <route.component {...props} routes={route.routes} />
      }}
    />
  );
}

function Tacos({ routes }) {
  return (
    <div>
      <h2>Tacos</h2>
      <ul>
        <li>
          <Link to="/tacos/bus">Bus</Link>
        </li>
        <li>
          <Link to="/tacos/cart">Cart</Link>
        </li>
      </ul>

      <Switch>
        {routes.map((route, i) => (
          <RouteWithSubRoutes key={i} {...route} />
        ))}
      </Switch>
    </div>
  );
}

render(<App />, document.getElementById("root"))

Query parameters 查询参数

 该示例其实本质是借用了浏览器内置的URLSearchParams，这个方法可以很方便的解析url参数，但这个存在兼容问题，放弃IE家族就没问题了。具体URLSearchParamsAPI，可参考MDN这段示例代码：

var paramsString = "q=URLUtils.searchParams&topic=api"
var searchParams = new URLSearchParams(paramsString);

searchParams.has("topic") === true; // true
searchParams.get("topic") === "api"; // true
searchParams.getAll("topic"); // ["api"]
searchParams.get("foo") === null; // true
searchParams.append("topic", "webdev");
searchParams.toString(); // "q=URLUtils.searchParams&topic=api&topic=webdev"
searchParams.set("topic", "More webdev");
searchParams.toString(); // "q=URLUtils.searchParams&topic=More+webdev"
searchParams.delete("topic");
searchParams.toString(); // "q=URLUtils.searchParams"

import React from "react";
import { render } from 'react-dom'
import {
  BrowserRouter as Router,
  Link,
  useLocation
} from "react-router-dom";



export default function App() {
  return (
    <Router>
      <QueryParamsDemo />
    </Router>
  );
}

//这里是重点
function useQuery() {
  return new URLSearchParams(useLocation().search);
}

function QueryParamsDemo() {
  let query = useQuery();
  return (
    <div>
      <div>
        <h2>Accounts</h2>
        <ul>
          <li>
            <Link to="/account?name=netflix">Netflix</Link>
          </li>
          <li>
            <Link to="/account?name=zillow-group">Zillow Group</Link>
          </li>
          <li>
            <Link to="/account?name=yahoo">Yahoo</Link>
          </li>
          <li>
            <Link to="/account?name=modus-create">Modus Create</Link>
          </li>
        </ul>

        <Child name={query.get("name")} />
      </div>
    </div>
  );
}

function Child({ name }) {
  return (
    <div>
      {name ? (
        <h3>
          The <code>name</code> in the query string is &quot;{name}
          &quot;
        </h3>
      ) : (
        <h3>There is no name in the query string</h3>
      )}
    </div>
  );
}

render(<App />, document.getElementById("root"))