1，Router 的结构

1，react-router 用于注入 history 上下文对象，但 history 对象是别人传递给它的。

2，react-router-dom 使用了 react-router，并传递创建 history 对象。

大致如下：

1，react-router-dom.js

import { createBrowserHistory } from "history"
import { Router } from "./react-router"export default class BrowserRouter extends Component {history = createBrowserHistory(this.props)render() {return <Router history={this.history}>{this.props.children}</Router>}
}

2，react-router.js

export default class Router extends Component {ctxValue = { //上下文中对象history: {},location : {},match : {},}render() {return <ctx.Provider value={this.ctxValue}>{this.props.children}</ctx.Provider>}
}

3，其他组件使用：

import { BrowserRouter as Router } from "./react-router-dom";export default function App() {return <Router></Router>
}

2，实现

项目目录

react-router-- index.js-- matchPath.js-- Router.js-- RouterContext.js
react-router-dom-- index.js-- BrowserRouter.js

2.1，react-router

1，matchPath.js

用于获取并组装 match 对象，参考 这篇文章。

2，Router.js

import React, { Component } from "react";
import PropTypes from "prop-types";
import ctx from "./RouterContext";
import matchPath from "./matchPath";export class Router extends Component {static propTypes = {history: PropTypes.object.isRequired,children: PropTypes.node,};state = {location: this.props.history.location, // location 作为状态，是因为切换路由时会发生变化。};componentDidMount() {this.unListen = this.props.history.listen((nextLocation, action) => {this.props.history.action = action;this.setState({location: nextLocation,});});}componentWillUnmount() {this.unListen();}ctxValue = {};render() {this.ctxValue.history = this.props.history;this.ctxValue.location = this.state.location;this.ctxValue.match = matchPath("/", this.state.location.pathname);return <ctx.Provider value={this.ctxValue}>{this.props.children}</ctx.Provider>;}
}

3，RouterContext.jsx

提供上下文对象。

import { createContext } from "react";const context = createContext();
context.displayName = "Router"; // 在 React 插件调试时，显示的名字。export default context;

4，index.jsx

export * from "./Router";

2.2，react-router-dom

BrowserRouter.jsx

import React, { Component } from "react";
import { createBrowserHistory } from "history";
import { Router } from "../react-router";export class BrowserRouter extends Component {history = createBrowserHistory();render() {return <Router history={this.history}>{this.props.children}</Router>;}
}

index.jsx

export * from "./BrowserRouter";

接下文实现 Route

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以上。