ERROR ReferenceError: React is not defined | Using React Components in Angular

Question

So basically I want to render one single React component (a notification component) into my Angular project. I created Notification.tsx

import * as React from 'react';
import { FunctionComponent, useEffect, useRef, useState } from 'react';
import { IconButton, Badge, Menu, List, ListItem, ListItemIcon, ListItemText, ListItemSecondaryAction, Avatar } from '@material-ui/core';
import { Notifications, Delete, Event, HourglassEmpty, Alarm } from '@material-ui/icons';
import { makeStyles } from '@material-ui/core/styles';
import { grey } from '@material-ui/core/colors';

export interface NotificationProps { }

export const NotificationComponent: FunctionComponent<NotificationProps> = (props: NotificationProps) => {
    return <div className={"row"}>
        <IconButton disableRipple={true} aria-label="notification" className="py-3 my-auto"
            onClick={handleNotificationMenuClick} aria-controls="notification-drop-down-menu"
            aria-haspopup="true">
            <Badge badgeContent={4} max={99} color="secondary">
                <Notifications />
            </Badge>
        </IconButton>
    </div>
};

A wrapper component NotificationWrapper.tsx

import { AfterViewInit, Component, ElementRef, OnChanges, OnDestroy, SimpleChanges, ViewChild, ViewEncapsulation } from '@angular/core';
import { NotificationComponent } from './Notification';
import * as React from 'react';
import * as ReactDOM from 'react-dom';

const containerElementName = 'notificationComponentTemplate';

@Component({
    selector: 'react-notification-component',
    template: `<span #${containerElementName}></span>`,
    encapsulation: ViewEncapsulation.None,
})
export class NotificationWrapper implements OnChanges, OnDestroy, AfterViewInit {
    @ViewChild(containerElementName, { static: false }) containerRef: ElementRef;

    constructor() { }

    ngOnChanges(changes: SimpleChanges): void {
        this.render();
    }

    ngAfterViewInit() {
        this.render();
    }

    ngOnDestroy() {
        ReactDOM.unmountComponentAtNode(this.containerRef.nativeElement);
    }

    private render() {
        ReactDOM.render(<div className={'notification-wrapper'}>
            <NotificationComponent />
        </div>, this.containerRef.nativeElement);
    }
}

Added this wrapper to app.module.ts's @NgModule

import { NotificationWrapper } from "../react-components/notification/NotificationWrapper";

@NgModule({
  declarations: [
    NotificationWrapper,
  ],
})

Used the notification wrapper selector as follows:

        <div class="col-sm-6">
          <react-notification-component></react-notification-component>
        </div>

Everything works fine when served locally and as I went through other similar questions on this site: I've added "jsx": "react" to tsconfig.json,

  plugins: [
    new webpack.ProvidePlugin({
      "React": "react",
    })
  ]

and

  externals: {
    'react': 'React'
  },

to webpack.config.js. Here's the whole file for reference.

// Work around for https://github.com/angular/angular-cli/issues/7200

const path = require('path');
const webpack = require('webpack');
// change the regex to include the packages you want to exclude
const regex = /firebase\/(app|firestore)/;

module.exports = {
  mode: 'production',
  entry: {
    // This is our Express server for Dynamic universal
    server: './server.ts'
  },
  externals: {
    './dist/server/main': 'require("./server/main")',
    'react': 'React'
  },
  target: 'node',
  node: {
    __dirname: false,
    __filename: false,
  },
  resolve: { extensions: ['.ts', '.js'] },
  target: 'node',
  mode: 'none',
  // this makes sure we include node_modules and other 3rd party libraries
  externals: [/node_modules/, function (context, request, callback) {
    // exclude firebase products from being bundled, so they will be loaded using require() at runtime.
    if (regex.test(request)) {
      return callback(null, 'commonjs ' + request);
    }
    callback();
  }],
  optimization: {
    minimize: false
  },
  output: {
    // Puts the output at the root of the dist folder
    path: path.join(__dirname, 'dist'),
    filename: '[name].js'
  },
  module: {
    noParse: /polyfills-.*\.js/,
    rules: [
      { test: /\.ts$/, loader: 'ts-loader' },
      {
        // Mark files inside `@angular/core` as using SystemJS style dynamic imports.
        // Removing this will cause deprecation warnings to appear.
        test: /(\\|\/)@angular(\\|\/)core(\\|\/).+\.js$/,
        parser: { system: true },
      },
    ]
  },
  plugins: [
    new webpack.ProvidePlugin({
      "React": "react",
    }),
    new webpack.ContextReplacementPlugin(
      // fixes WARNING Critical dependency: the request of a dependency is an expression
      /(.+)?angular(\\|\/)core(.+)?/,
      path.join(__dirname, 'src'), // location of your src
      {} // a map of your routes
    ),
    new webpack.ContextReplacementPlugin(
      // fixes WARNING Critical dependency: the request of a dependency is an expression
      /(.+)?express(\\|\/)(.+)?/,
      path.join(__dirname, 'src'),
      {}
    )
  ]
};

My problem is, when I build my app, the notification component is not rendered and I get this error in console ERROR ReferenceError: React is not defined. Is there anything that I missed? Thanks in advance.

hmarchadour · Accepted Answer · 2021-07-02 08:30:47Z

7

I think it's a typical unwanted optimization that remove React in the final js (React isn't directly used)

Try to call a method or an attribute on React like React.version :

import {
  OnChanges,
  ViewChild
} from '@angular/core';
import { MyComponent } from './react/MyComponent';
import * as React from 'react';
import * as ReactDOM from 'react-dom';

const containerElementName = 'myReactComponentContainer';

@Component({
  ...
})
export class MyComponent implements OnChanges {

  @ViewChild(containerElementName) containerRef: ElementRef;
  ngOnChanges(changes: SimpleChanges): void {
    this.render();
  }

  private render() {
    React.version;
    ReactDOM.render(<MyReactComponent />,     this.containerRef.nativeElement);
  }
}

answered Jul 2, 2021 at 8:30

hmarchadour

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1 Comment

Harshal Yeole Over a year ago

This one solved my issue and didn't have to change this Set aot and buildOptimizer to false in angular.json

Durk · Accepted Answer · 2021-03-10 07:39:07Z

6

Add the following to tsconfig.json

"compilerOptions": {
  "allowSyntheticDefaultImports": true,
  "jsx": "react",
}

Set aot and buildOptimizer to false in angular.json

Replace

import * as React from 'react';
import * as ReactDOM from 'react-dom'

with

import React from 'react';
import ReactDOM from 'react-dom';

answered Mar 10, 2021 at 7:39

Durk

743 bronze badges

3 Comments

RossyBergg Over a year ago

Coming across the same problem, tho this solution didnt work for me, only way I can get it to work is by setting "optimization" in angular.json to false. But not something I really want to do :(

Durk Over a year ago

set aot and buildOptimizer to false

RossyBergg Over a year ago

I did, you already said that in your solution, upgrading Angular 11 from 10 worked with your solution in my case

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