React-router 4 按需加载的实现方式及原理详解

route3中实现按需加载只需要按照下面代码的方式实现就可以了。

const about = (location, cb) => {
  require.ensure([], require => {
    cb(null, require('../Component/about').default)
  },'about')
}

//配置route
<Route path="helpCenter" getComponent={about} />

import React from 'react';
import PropTypes from 'prop-types';

class Bundle extends React.Component {
 state = {
  // short for "module" but that's a keyword in js, so "mod"
  mod: null
 }

 componentWillMount() {
  // 加载初始状态
  this.load(this.props);
 }

 componentWillReceiveProps(nextProps) {
  if (nextProps.load !== this.props.load) {
   this.load(nextProps);
  }
 }

 load(props) {
  // 重置状态
  this.setState({
   mod: null
  });
  // 传入组件的组件
  props.load((mod) => {
   this.setState({
    // handle both es imports and cjs
    mod: mod.default "htmlcode">

import aContainer from 'bundle-loader"htmlcode">

 render() {
  return (
   <div>
    <h1>Welcome!</h1>
    <Route path="/about" component={About}/>
    <Route path="/dashboard" component={A}/>
   </div>
  )
 }


3.router4按需加载方方式解析


(1).首先解释一下按需加载，通俗的将就是我当前的location在Home,那么我只应该加载Home的东西，而不应该去加载About等等其他的。
(2).Bundle.js这个文件的作用
先看这段代码：


module.exports = function (cb) {
  __webpack_require__.e/* require.ensure */(2).then((function (require) {
    cb(__webpack_require__(305));
  }).bind(null, __webpack_require__)).catch(__webpack_require__.oe);
};


这里是我们通过import loadDashboard from 'bundle-loader"htmlcode">

 {
   // 匹配routers下面所有文件
   // ([^/]+)\/"htmlcode">

var loaderUtils = require("loader-utils");

module.exports = function() {};
module.exports.pitch = function(remainingRequest) {
  this.cacheable && this.cacheable();
  var query = loaderUtils.getOptions(this) || {};
  if(query.name) {
    var options = {
      context: query.context || this.options.context,
      regExp: query.regExp
    };
    var chunkName = loaderUtils.interpolateName(this, query.name, options);
    var chunkNameParam = ", " + JSON.stringify(chunkName);
  } else {
    var chunkNameParam = '';
  }
  var result;
  if(query.lazy) {
    result = [
      "module.exports = function(cb) {\n",
      "  require.ensure([], function(require) {\n",
      "    cb(require(", loaderUtils.stringifyRequest(this, "!!" + remainingRequest), "));\n",
      "  }" + chunkNameParam + ");\n",
      "}"];
  } else {
    result = [
      "var cbs = [], \n",
      "  data;\n",
      "module.exports = function(cb) {\n",
      "  if(cbs) cbs.push(cb);\n",
      "  else cb(data);\n",
      "}\n",
      "require.ensure([], function(require) {\n",
      "  data = require(", loaderUtils.stringifyRequest(this, "!!" + remainingRequest), ");\n",
      "  var callbacks = cbs;\n",
      "  cbs = null;\n",
      "  for(var i = 0, l = callbacks.length; i < l; i++) {\n",
      "    callbacks[i](data);\n",
      "  }\n",
      "}" + chunkNameParam + ");"];
  }
  return result.join("");
}

/*
Output format:

  var cbs = [],
    data;
  module.exports = function(cb) {
    if(cbs) cbs.push(cb);
    else cb(data);
  }
  require.ensure([], function(require) {
    data = require("xxx");
    var callbacks = cbs;
    cbs = null;
    for(var i = 0, l = callbacks.length; i < l; i++) {
      callbacks[i](data);
    }
  });

*/



2.A的源码


import React from 'react';
import PropTypes from 'prop-types';
import * as reactRedux from 'react-redux';
import BaseContainer from '../../../containers/ReactBaseContainer';

class A extends BaseContainer {
 constructor(props) {
  super(props);
  this.renderCustom = function renderCustom() {
   return (
    <div >
     Hello world In A
    </div>
   );
  };
 }
 render() {
  // 返回父级view
  return super.render();
 }
}

A.propTypes = {
 dispatch: PropTypes.func,
};

function mapStateToProps(state) {
 return { state };
}

export default reactRedux.connect(mapStateToProps)(A);




3.route.js的源码


import React from 'react';
import { BrowserRouter, Switch, Link } from 'react-router-dom';
import { Route } from 'react-router';
import PostContainer from '../containers/PostsContainer';
// 设置trunk文件的名字 the basename of the resource
import aContainer from './containers/A';
import bContainer from './containers/B';
import cContainer from './containers/C';
import Bundle from '../utils/Bundle';

const A = () => (
 <Bundle load={aContainer}>
  {Component => <Component />}
 </Bundle>
)

const app = () =>
 <div>
  {/* path = "/about" */}
  {/* "/about/" 可以，但"/about/1"就不可以了 exact 配置之后，需要路径绝对匹配,多个斜杠没有关系，这里直接在浏览器里面设置还有问题*/}
  {/* path = "/about/" */}
  {/* "/about/1" 可以，但"/about"就不可以了 用了strict，path要大于等于的关系，少一个斜杠都不行 */}
  {/* exact 和 strick 都用了就必须一模一样，连斜杠都一样 */}
  <Link to="/about/"> Link to about</Link>
  <Route path="/" component={PostContainer} />
  <Route path="/about/" component={A} />
  {/* <Route path="/home" component={B} />
  <Route component={C} /> */}
 </div>
;
export default function () {
 // 用来判断本地浏览器是否支持刷新
 const supportsHistory = 'pushState' in window.history;
 return (
  <BrowserRouter forceRefresh={!supportsHistory} keyLength={12}>
   <div>
    {app()}
   </div>
  </BrowserRouter>

 );
}




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