我在流程类型检查中收到以下错误。

Cannot call ReactDOM.render with document.getElementById(...) bound to container because null [1] is
incompatible with Element [2].

     src/index.js
      26│       </Switch>
      27│     </ScrollToTop>
      28│   </BrowserRouter>
      29│ </Provider>, document.getElementById("root"));
      30│

     /private/tmp/flow/flowlib_174a8121/dom.js
 [1] 646│   getElementById(elementId: string): HTMLElement | null;

     /private/tmp/flow/flowlib_174a8121/react-dom.js
 [2]  18│     container: Element,

代码如下。

// @flow
"use strict";
import React from "react";
import ReactDOM from "react-dom";
import {createStore, applyMiddleware} from "redux";
import {Provider} from "react-redux";
import {BrowserRouter, Switch, Route} from "react-router-dom";
import Home from "./components/home";
import Detail from "./components/detail";
import LevelOfGame from "./components/level-of-game";
import NotFound from "./components/not-found";
import ScrollToTop from "./components/scroll-to-top";

import reducers from "./reducers";

const createStoreWithMiddleware = applyMiddleware()(createStore);

ReactDOM.render(<Provider store={createStoreWithMiddleware(reducers)}>
  <BrowserRouter>
    <ScrollToTop>
      <Switch>
        <Route exact path="/" component={Home}/>
        <Route path="/detail/:detailId" component={Detail}/>
        <Route path="/level-of-game" component={LevelOfGame}/>
        <Route path="*" component={NotFound} status={404}/>
      </Switch>
    </ScrollToTop>
  </BrowserRouter>
</Provider>, document.getElementById("root"));

我相信我必须以某种方式指定类型getElementById。

因此，我通过存储document.getElementById("root");在具有类型规范的常量变量中来修复错误：

const root: any = document.getElementById("root");

该错误已修复，希望对其他人有用，但我很想了解造成此错误的原因。谁能告诉我这是什么吗？