boolean bubbles
boolean cancelable
DOMEventTarget currentTarget
boolean defaultPrevented
number eventPhase
boolean isTrusted
DOMEvent nativeEvent
void preventDefault()
boolean isDefaultPrevented()
void stopPropagation()
boolean isPropagationStopped()
void persist()
DOMEventTarget target
number timeStamp
string type

function onClick(event) {
  console.log(event); // => nullified object.
  console.log(event.type); // => "click"
  const eventType = event.type; // => "click"
  setTimeout(function() {
    console.log(event.type); // => null
    console.log(eventType); // => "click"
  }, 0);
  this.setState({clickEvent: event});
  // 你仍然可以導(dǎo)出事件屬性
  this.setState({eventType: event.type});
}

number pointerId
number width
number height
number pressure
number tangentialPressure
number tiltX
number tiltY
number twist
string pointerType
boolean isPrimary

import ReactTestUtils from 'react-dom/test-utils'; // ES6
var ReactTestUtils = require('react-dom/test-utils'); // ES5 使用 npm 的方式

class Counter extends React.Component {
  constructor(props) {
    super(props);
    this.state = {count: 0};
    this.handleClick = this.handleClick.bind(this);
  }
  componentDidMount() {
    document.title = `You clicked ${this.state.count} times`;
  }
  componentDidUpdate() {
    document.title = `You clicked ${this.state.count} times`;
  }
  handleClick() {
    this.setState(state => ({
      count: state.count + 1,
    }));
  }
  render() {
    return (
      <div>
        <p>You clicked {this.state.count} times</p>
        <button onClick={this.handleClick}>
          Click me
        </button>
      </div>
    );
  }
}

import React from 'react';
import ReactDOM from 'react-dom';
import { act } from 'react-dom/test-utils';
import Counter from './Counter';
let container;
beforeEach(() => {
  container = document.createElement('div');
  document.body.appendChild(container);
});
afterEach(() => {
  document.body.removeChild(container);
  container = null;
});
it('can render and update a counter', () => {
  // 首先測試 render 和 componentDidMount
  act(() => {
    ReactDOM.render(<Counter />, container);
  });
  const button = container.querySelector('button');
  const label = container.querySelector('p');
  expect(label.textContent).toBe('You clicked 0 times');
  expect(document.title).toBe('You clicked 0 times');
  // 再測試 render 和 componentDidUpdate
  act(() => {
    button.dispatchEvent(new MouseEvent('click', {bubbles: true}));
  });
  expect(label.textContent).toBe('You clicked 1 times');
  expect(document.title).toBe('You clicked 1 times');
});

scryRenderedComponentsWithType(
  tree,
  componentClass
)

import TestRenderer from 'react-test-renderer';
function Link(props) {
  return <a href={props.page}>{props.children}</a>;
}
const testRenderer = TestRenderer.create(
  <Link page="https://www.facebook.com/">Facebook</Link>
);
console.log(testRenderer.toJSON());