问正在获取此错误...invariant.js:42未捕获错误:应将`onClick`侦听器作为函数，但却获得了` `string` `类型的值

EN

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';

var questionNum = 1;

class App extends Component {
  render() {
    return (
      <div className="App">
        <div>
          <header className="App-header">
            <img src={logo} className="App-logo" alt="logo" />
            <h1 className="App-title">Welcome to React</h1>
          </header>
          <p className="App-intro">
            To get started, edit <code>src/App.js</code> and save to reload.
          </p>
        </div>
        <form>
          Give your quiz a title:<br />
          <input type="text" name="quizTitle" /><br />
          Who's the author?<br />
          <input type="text" name="author" /><br />
          Now let's add some questions...<br />
          <form className="quesitons">
            <div id={"questions" + questionNum}>
              Question {questionNum}<br />
              <input type="text" name={"question" + questionNum}/><br />
              Answers<br />
              Check the box(es) for the correct answer(s).<br />
              <input type="checkbox" name={"question" + questionNum + "Answer1Box"} />
              <label for={"question" + questionNum + "Answer1"}><input type="text" name={"question" + questionNum + "Answer1"}/></label><br />
              <input type="checkbox" name={"question" + questionNum + "Answer2Box"} />
              <label for={"question" + questionNum + "Answer2"}><input type="text" name={"question" + questionNum + "Answer2"}/></label><br />
              <input type="checkbox" name={"question" + questionNum + "Answer3Box"} />
              <label for={"question" + questionNum + "Answer3"}><input type="text" name={"question" + questionNum + "Answer3"}/></label><br />
              <input type="checkbox" name={"question" + questionNum + "Answer4Box"} />
              <label for={"question" + questionNum + "Answer4"}><input type="text" name={"question" + questionNum + "Answer4"}/></label><br />
            </div>
            <div id="container"></div>
          </form>
        </form>
        <button id="addQuestionButton" onClick='addQuestion ()'>Add Question</button>
      </div>
    );
  }
}

function addQuestion () {
  questionNum++;
  console.log(questionNum + "that is the question number");

  var div = document.createElement('div');

    div.className = '{"questions" + questionNum}';

    div.innerHTML =
        'Question {questionNum}<br />\
        <input type="text" name={"question" + questionNum}/><br />\
        Answers<br />\
        Check the box(es) for the correct answer(s).<br />\
        <input type="checkbox" name={"question" + questionNum + "Answer1Box"} />\
        <label for={"question" + questionNum + "Answer1"}><input type="text" name={"question" + questionNum + "Answer1"}/></label><br />\
        <input type="checkbox" name={"question" + questionNum + "Answer2Box"} />\
        <label for={"question" + questionNum + "Answer2"}><input type="text" name={"question" + questionNum + "Answer2"}/></label><br />\
        <input type="checkbox" name={"question" + questionNum + "Answer3Box"} />\
        <label for={"question" + questionNum + "Answer3"}><input type="text" name={"question" + questionNum + "Answer3"}/></label><br />\
        <input type="checkbox" name={"question" + questionNum + "Answer4Box"} />\
        <label for={"question" + questionNum + "Answer4"}><input type="text" name={"question" + questionNum + "Answer4"}/></label><br />\
        ';

    document.getElementsByClassName('questions').appendChild(div);
}

export default App;

invariant.js:42 Uncaught Error: Expected `onClick` listener to be a function, instead got a value of `string` type.

Uncaught Error: Expected `onClick` listener to be a function, instead got a value of `string` type.
    at invariant (invariant.js:42)
    at getListener (react-dom.development.js:680)
    at listenerAtPhase (react-dom.development.js:981)
    at accumulateDirectionalDispatches (react-dom.development.js:1004)
    at traverseTwoPhase (react-dom.development.js:924)
    at accumulateTwoPhaseDispatchesSingle (react-dom.development.js:1020)
    at forEachAccumulated (react-dom.development.js:562)
    at accumulateTwoPhaseDispatches (react-dom.development.js:1063)
    at Object.extractEvents (react-dom.development.js:4396)
    at extractEvents (react-dom.development.js:697)
    at runExtractedEventsInBatch (react-dom.development.js:731)
    at handleTopLevel (react-dom.development.js:4476)
    at batchedUpdates$1 (react-dom.development.js:16659)
    at batchedUpdates (react-dom.development.js:2131)
    at dispatchEvent (react-dom.development.js:4555)
    at interactiveUpdates$1 (react-dom.development.js:16714)
    at interactiveUpdates (react-dom.development.js:2150)
    at dispatchInteractiveEvent (react-dom.development.js:4532)