test-eventtarget.js

// Flags: --expose-internals --no-warnings
'use strict';

const common = require('../common');
const {
  Event,
  EventTarget,
  NodeEventTarget,
} = require('internal/event_target');

const {
  ok,
  deepStrictEqual,
  strictEqual,
  throws,
} = require('assert');

const { once, on } = require('events');

// The globals are defined.
ok(Event);
ok(EventTarget);

// First, test Event
{
  const ev = new Event('foo');
  strictEqual(ev.type, 'foo');
  strictEqual(ev.cancelable, false);
  strictEqual(ev.defaultPrevented, false);
  strictEqual(typeof ev.timeStamp, 'number');

  // Compatibility properties with the DOM
  deepStrictEqual(ev.composedPath(), []);
  strictEqual(ev.returnValue, true);
  strictEqual(ev.bubbles, false);
  strictEqual(ev.composed, false);
  strictEqual(ev.isTrusted, false);
  strictEqual(ev.eventPhase, 0);
  strictEqual(ev.cancelBubble, false);

  // Not cancelable
  ev.preventDefault();
  strictEqual(ev.defaultPrevented, false);
}
{
  // No argument behavior - throw TypeError
  throws(() => {
    new Event();
  }, TypeError);
  // Too many arguments passed behavior - ignore additional arguments
  const ev = new Event('foo', {}, {});
  strictEqual(ev.type, 'foo');
}
{
  const ev = new Event('foo');
  strictEqual(ev.cancelBubble, false);
  ev.cancelBubble = true;
  strictEqual(ev.cancelBubble, true);
}
{
  const ev = new Event('foo');
  strictEqual(ev.cancelBubble, false);
  ev.stopPropagation();
  strictEqual(ev.cancelBubble, true);
}
{
  const ev = new Event('foo');
  strictEqual(ev.cancelBubble, false);
  ev.cancelBubble = 'some-truthy-value';
  strictEqual(ev.cancelBubble, true);
}
{
  const ev = new Event('foo', { cancelable: true });
  strictEqual(ev.type, 'foo');
  strictEqual(ev.cancelable, true);
  strictEqual(ev.defaultPrevented, false);

  ev.preventDefault();
  strictEqual(ev.defaultPrevented, true);
}
{
  const ev = new Event('foo');
  deepStrictEqual(Object.keys(ev), ['isTrusted']);
}
{
  const eventTarget = new EventTarget();

  const ev1 = common.mustCall(function(event) {
    strictEqual(event.type, 'foo');
    strictEqual(this, eventTarget);
    strictEqual(event.eventPhase, 2);
  }, 2);

  const ev2 = {
    handleEvent: common.mustCall(function(event) {
      strictEqual(event.type, 'foo');
      strictEqual(this, ev2);
    })
  };

  eventTarget.addEventListener('foo', ev1);
  eventTarget.addEventListener('foo', ev2, { once: true });
  ok(eventTarget.dispatchEvent(new Event('foo')));
  eventTarget.dispatchEvent(new Event('foo'));

  eventTarget.removeEventListener('foo', ev1);
  eventTarget.dispatchEvent(new Event('foo'));
}
{
  // event subclassing
  const SubEvent = class extends Event {};
  const ev = new SubEvent('foo');
  const eventTarget = new EventTarget();
  const fn = common.mustCall((event) => strictEqual(event, ev));
  eventTarget.addEventListener('foo', fn, { once: true });
  eventTarget.dispatchEvent(ev);
}
{
  const eventTarget = new NodeEventTarget();
  strictEqual(eventTarget.listenerCount('foo'), 0);
  deepStrictEqual(eventTarget.eventNames(), []);

  const ev1 = common.mustCall(function(event) {
    strictEqual(event.type, 'foo');
    strictEqual(this, eventTarget);
  }, 2);

  const ev2 = {
    handleEvent: common.mustCall(function(event) {
      strictEqual(event.type, 'foo');
      strictEqual(this, ev2);
    })
  };

  eventTarget.addEventListener('foo', ev1);
  eventTarget.addEventListener('foo', ev2, { once: true });
  strictEqual(eventTarget.listenerCount('foo'), 2);
  ok(eventTarget.dispatchEvent(new Event('foo')));
  strictEqual(eventTarget.listenerCount('foo'), 1);
  eventTarget.dispatchEvent(new Event('foo'));

  eventTarget.removeEventListener('foo', ev1);
  strictEqual(eventTarget.listenerCount('foo'), 0);
  eventTarget.dispatchEvent(new Event('foo'));
}


{
  const eventTarget = new EventTarget();
  const event = new Event('foo', { cancelable: true });
  eventTarget.addEventListener('foo', (event) => event.preventDefault());
  ok(!eventTarget.dispatchEvent(event));
}
{
  // Adding event listeners with a boolean useCapture
  const eventTarget = new EventTarget();
  const event = new Event('foo');
  const fn = common.mustCall((event) => strictEqual(event.type, 'foo'));
  eventTarget.addEventListener('foo', fn, false);
  eventTarget.dispatchEvent(event);
}
{
  const eventTarget = new NodeEventTarget();
  strictEqual(eventTarget.listenerCount('foo'), 0);
  deepStrictEqual(eventTarget.eventNames(), []);

  const ev1 = common.mustCall((event) => {
    strictEqual(event.type, 'foo');
  }, 2);

  const ev2 = {
    handleEvent: common.mustCall((event) => {
      strictEqual(event.type, 'foo');
    })
  };

  strictEqual(eventTarget.on('foo', ev1), eventTarget);
  strictEqual(eventTarget.once('foo', ev2, { once: true }), eventTarget);
  strictEqual(eventTarget.listenerCount('foo'), 2);
  eventTarget.dispatchEvent(new Event('foo'));
  strictEqual(eventTarget.listenerCount('foo'), 1);
  eventTarget.dispatchEvent(new Event('foo'));

  strictEqual(eventTarget.off('foo', ev1), eventTarget);
  strictEqual(eventTarget.listenerCount('foo'), 0);
  eventTarget.dispatchEvent(new Event('foo'));
}

{
  const eventTarget = new NodeEventTarget();
  strictEqual(eventTarget.listenerCount('foo'), 0);
  deepStrictEqual(eventTarget.eventNames(), []);

  const ev1 = common.mustCall((event) => {
    strictEqual(event.type, 'foo');
  }, 2);

  const ev2 = {
    handleEvent: common.mustCall((event) => {
      strictEqual(event.type, 'foo');
    })
  };

  eventTarget.addListener('foo', ev1);
  eventTarget.once('foo', ev2, { once: true });
  strictEqual(eventTarget.listenerCount('foo'), 2);
  eventTarget.dispatchEvent(new Event('foo'));
  strictEqual(eventTarget.listenerCount('foo'), 1);
  eventTarget.dispatchEvent(new Event('foo'));

  eventTarget.removeListener('foo', ev1);
  strictEqual(eventTarget.listenerCount('foo'), 0);
  eventTarget.dispatchEvent(new Event('foo'));
}

{
  const eventTarget = new NodeEventTarget();
  strictEqual(eventTarget.listenerCount('foo'), 0);
  deepStrictEqual(eventTarget.eventNames(), []);

  // Won't actually be called.
  const ev1 = () => {};

  // Won't actually be called.
  const ev2 = { handleEvent() {} };

  eventTarget.addListener('foo', ev1);
  eventTarget.addEventListener('foo', ev1);
  eventTarget.once('foo', ev2, { once: true });
  eventTarget.once('foo', ev2, { once: false });
  eventTarget.on('bar', ev1);
  strictEqual(eventTarget.listenerCount('foo'), 2);
  strictEqual(eventTarget.listenerCount('bar'), 1);
  deepStrictEqual(eventTarget.eventNames(), ['foo', 'bar']);
  eventTarget.removeAllListeners('foo');
  strictEqual(eventTarget.listenerCount('foo'), 0);
  strictEqual(eventTarget.listenerCount('bar'), 1);
  deepStrictEqual(eventTarget.eventNames(), ['bar']);
  eventTarget.removeAllListeners();
  strictEqual(eventTarget.listenerCount('foo'), 0);
  strictEqual(eventTarget.listenerCount('bar'), 0);
  deepStrictEqual(eventTarget.eventNames(), []);
}

{
  const uncaughtException = common.mustCall((err, event) => {
    strictEqual(err.message, 'boom');
    strictEqual(event.type, 'foo');
  }, 4);

  // Whether or not the handler function is async or not, errors
  // are routed to uncaughtException
  process.on('error', uncaughtException);

  const eventTarget = new EventTarget();

  const ev1 = async () => { throw new Error('boom'); };
  const ev2 = () => { throw new Error('boom'); };
  const ev3 = { handleEvent() { throw new Error('boom'); } };
  const ev4 = { async handleEvent() { throw new Error('boom'); } };

  // Errors in a handler won't stop calling the others.
  eventTarget.addEventListener('foo', ev1, { once: true });
  eventTarget.addEventListener('foo', ev2, { once: true });
  eventTarget.addEventListener('foo', ev3, { once: true });
  eventTarget.addEventListener('foo', ev4, { once: true });

  eventTarget.dispatchEvent(new Event('foo'));
}

{
  const eventTarget = new EventTarget();

  // Once handler only invoked once
  const ev = common.mustCall((event) => {
    throws(() => eventTarget.dispatchEvent(new Event('foo')), {
      code: 'ERR_EVENT_RECURSION'
    });
  });

  // Errors in a handler won't stop calling the others.
  eventTarget.addEventListener('foo', ev);

  eventTarget.dispatchEvent(new Event('foo'));
}

{
  // Coercion to string works
  strictEqual((new Event(1)).type, '1');
  strictEqual((new Event(false)).type, 'false');
  strictEqual((new Event({})).type, String({}));

  const target = new EventTarget();

  [
    'foo',
    {},  // No type event
    undefined,
    1,
    false
  ].forEach((i) => {
    throws(() => target.dispatchEvent(i), {
      code: 'ERR_INVALID_ARG_TYPE'
    });
  });

  [
    'foo',
    1,
    {},  // No handleEvent function
    false,
    undefined
  ].forEach((i) => {
    throws(() => target.addEventListener('foo', i), {
      code: 'ERR_INVALID_ARG_TYPE'
    });
  });

  [
    'foo',
    1,
    {},  // No handleEvent function
    false,
    undefined
  ].forEach((i) => {
    throws(() => target.removeEventListener('foo', i), {
      code: 'ERR_INVALID_ARG_TYPE'
    });
  });
}

{
  const target = new EventTarget();
  once(target, 'foo').then(common.mustCall());
  target.dispatchEvent(new Event('foo'));
}

{
  const target = new NodeEventTarget();

  process.on('warning', common.mustCall((warning) => {
    ok(warning instanceof Error);
    strictEqual(warning.name, 'MaxListenersExceededWarning');
    strictEqual(warning.target, target);
    strictEqual(warning.count, 2);
    strictEqual(warning.type, 'foo');
    ok(warning.message.includes(
      '2 foo listeners added to NodeEventTarget'));
  }));

  strictEqual(target.getMaxListeners(), NodeEventTarget.defaultMaxListeners);
  target.setMaxListeners(1);
  target.on('foo', () => {});
  target.on('foo', () => {});
}

{
  const target = new EventTarget();
  const event = new Event('foo');
  event.stopImmediatePropagation();
  target.addEventListener('foo', common.mustNotCall());
  target.dispatchEvent(event);
}

{
  const target = new EventTarget();
  const event = new Event('foo');
  target.addEventListener('foo', common.mustCall((event) => {
    event.stopImmediatePropagation();
  }));
  target.addEventListener('foo', common.mustNotCall());
  target.dispatchEvent(event);
}

{
  const target = new EventTarget();
  const event = new Event('foo');
  target.addEventListener('foo', common.mustCall((event) => {
    event.stopImmediatePropagation();
  }));
  target.addEventListener('foo', common.mustNotCall());
  target.dispatchEvent(event);
}

{
  const target = new EventTarget();
  const event = new Event('foo');
  strictEqual(event.target, null);
  target.addEventListener('foo', common.mustCall((event) => {
    strictEqual(event.target, target);
    strictEqual(event.currentTarget, target);
    strictEqual(event.srcElement, target);
  }));
  target.dispatchEvent(event);
}

{
  const target1 = new EventTarget();
  const target2 = new EventTarget();
  const event = new Event('foo');
  target1.addEventListener('foo', common.mustCall((event) => {
    throws(() => target2.dispatchEvent(event), {
      code: 'ERR_EVENT_RECURSION'
    });
  }));
  target1.dispatchEvent(event);
}

{
  const target = new EventTarget();
  const a = common.mustCall(() => target.removeEventListener('foo', a));
  const b = common.mustCall(2);

  target.addEventListener('foo', a);
  target.addEventListener('foo', b);

  target.dispatchEvent(new Event('foo'));
  target.dispatchEvent(new Event('foo'));
}

{
  const target = new EventTarget();
  const a = common.mustCall(3);

  target.addEventListener('foo', a, { capture: true });
  target.addEventListener('foo', a, { capture: false });

  target.dispatchEvent(new Event('foo'));
  target.removeEventListener('foo', a, { capture: true });
  target.dispatchEvent(new Event('foo'));
  target.removeEventListener('foo', a, { capture: false });
  target.dispatchEvent(new Event('foo'));
}

{
  const target = new EventTarget();
  strictEqual(target.toString(), '[object EventTarget]');
  const event = new Event();
  strictEqual(event.toString(), '[object Event]');
}
{
  const target = new EventTarget();
  const ev = new Event('toString');
  const fn = common.mustCall((event) => strictEqual(event.type, 'toString'));
  target.addEventListener('toString', fn);
  target.dispatchEvent(ev);
}
{
  const target = new EventTarget();
  const ev = new Event('__proto__');
  const fn = common.mustCall((event) => strictEqual(event.type, '__proto__'));
  target.addEventListener('__proto__', fn);
  target.dispatchEvent(ev);
}

(async () => {
  // test NodeEventTarget async-iterability
  const emitter = new NodeEventTarget();
  const event = new Event('foo');
  const interval = setInterval(() => emitter.dispatchEvent(event), 0);
  let count = 0;
  for await (const [ item ] of on(emitter, 'foo')) {
    count++;
    strictEqual(item.type, 'foo');
    if (count > 5) {
      break;
    }
  }
  clearInterval(interval);
})().then(common.mustCall());