jsdom: dispatchEvent/addEventListener doesn't seem to work

Question

Summary:

I am attempting to test a React component that listens to native DOM events in its componentWillMount.

I'm finding that jsdom (@8.4.0) doesn't work as expected when it comes to dispatching events and adding event listeners.

The simplest bit of code I can extract:

window.addEventListener('click', () => {
  throw new Error("success")
})

const event = new Event('click')
document.dispatchEvent(event)

throw new Error('failure')

This throws "failure".

Context:

At risk of the above being an XY problem, I want to provide more context.

Here is an extracted/simplified version of the component I'm trying to test. You can see it working on Webpackbin.

import React from 'react'

export default class Example extends React.Component {
  constructor() {
    super()
    this._onDocumentClick = this._onDocumentClick.bind(this)
  }

  componentWillMount() {
    this.setState({ clicked: false })
    window.addEventListener('click', this._onDocumentClick)
  }

  _onDocumentClick() {
    const clicked = this.state.clicked || false
    this.setState({ clicked: !clicked })
  }


  render() {
    return <p>{JSON.stringify(this.state.clicked)}</p>
  }
}

Here is the test I'm trying to write.

import React from 'react'
import ReactDOM from 'react-dom'
import { mount } from 'enzyme'

import Example from '../src/example'

describe('test', () => {
  it('test', () => {
    const wrapper = mount(<Example />)

    const event = new Event('click')
    document.dispatchEvent(event)

    // at this point, I expect the component to re-render,
    // with updated state.

    expect(wrapper.text()).to.match(/true/)
  })
})

Just for completeness, here is my test_helper.js which initializes jsdom:

import { jsdom } from 'jsdom'
import chai from 'chai'

const doc = jsdom('<!doctype html><html><body></body></html>')
const win = doc.defaultView

global.document = doc
global.window = win

Object.keys(window).forEach((key) => {
  if (!(key in global)) {
    global[key] = window[key]
  }
})

Reproduction case:

I have a repro case here: https://github.com/jbinto/repro-jsdom-events-not-firing:

git clone https://github.com/jbinto/repro-jsdom-events-not-firing.git
cd repro-jsdom-events-not-firing
npm install
npm test

awesome question structure + repo – AndrewMcLagan Dec 02 '20 at 04:12 — AndrewMcLagan, Dec 02 '20 at 04:12

score 14 · Answer 1 · answered Apr 22 '16 at 22:28

You're dispatching the event to document so window won't see it because by default it won't bubble up. You need to create the event with bubbles set to true. Example:

var jsdom = require("jsdom");

var document = jsdom.jsdom("");
var window = document.defaultView;

window.addEventListener('click', function (ev) {
  console.log('window click', ev.target.constructor.name,
              ev.currentTarget.constructor.name);
});

document.addEventListener('click', function (ev) {
  console.log('document click', ev.target.constructor.name,
              ev.currentTarget.constructor.name);
});

console.log("not bubbling");

var event = new window.Event("click");
document.dispatchEvent(event);

console.log("bubbling");

event = new window.Event("click", {bubbles: true});
document.dispatchEvent(event);

`new window.Event("click");` ermagerd. `doc.createEvent('MouseEvents').initEvent('click', true, true)` returns undefined in jsdom... 1.5hrs to find your answer O.o — Larry, Jun 30 '16 at 11:43

score 7 · Accepted Answer · answered Jun 20 '16 at 14:26

The problem here was that the jsdom-provided document isn't actually getting used by Enzyme tests.

Enzyme uses renderIntoDocument from React.TestUtils.

https://github.com/facebook/react/blob/510155e027d56ce3cf5c890c9939d894528cf007/src/test/ReactTestUtils.js#L85

{
  renderIntoDocument: function(instance) {
    var div = document.createElement('div');
    // None of our tests actually require attaching the container to the
    // DOM, and doing so creates a mess that we rely on test isolation to
    // clean up, so we're going to stop honoring the name of this method
    // (and probably rename it eventually) if no problems arise.
    // document.documentElement.appendChild(div);
    return ReactDOM.render(instance, div);
  },
// ...
}

This means all of our Enzyme tests are not executed against the jsdom-provided document, but instead into a div node detached from any document.

Enzyme only uses the jsdom-provided document for static methods, e.g. getElementById etc. It is not used to store/operate on DOM elements.

In order to do these kinds of tests I resorted to actually calling ReactDOM.render, and asserting on the output using DOM methods.

score -1 · Answer 3 · answered Jul 14 '17 at 00:04

Code: https://github.com/LVCarnevalli/create-react-app/blob/master/src/components/datepicker

Link: ReactTestUtils.Simulate can't trigger event bind by addEventListener?

Component:

componentDidMount() {   
 ReactDOM.findDOMNode(this.datePicker.refs.input).addEventListener("change", (event) => {
    const value = event.target.value;
    this.handleChange(Moment(value).toISOString(), value);
  });
}

Test:

it('change empty value date picker', () => {
    const app = ReactTestUtils.renderIntoDocument(<Datepicker />);
    const datePicker = ReactDOM.findDOMNode(app.datePicker.refs.input);
    const value = "";

    const event = new Event("change");
    datePicker.value = value;
    datePicker.dispatchEvent(event);

    expect(app.state.formattedValue).toEqual(value);
});

jsdom: dispatchEvent/addEventListener doesn't seem to work

3 Answers3

Linked