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benjamingr wants to merge 3 commits into from
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events: support event handlers #33646

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89eaf9c
events: support event handlers
benjamingr May 29, 2020
8ac4425
fixup! lint
benjamingr May 29, 2020
076b122
Update test/parallel/test-eventtarget.js
benjamingr Jun 21, 2020
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events: support event handlers
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@benjamingr
benjamingr committed Jun 6, 2020
commit 89eaf9ce6064c7ce694c38cab67913b704615abc
21 changes: 19 additions & 2 deletions lib/internal/event_target.js
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Original file line number Diff line number Diff line change
Expand Up @@ -445,10 +445,27 @@ function emitUnhandledRejectionOrErr(that, err, event) {
process.emit('error', err, event);
}

// EventEmitter-ish API:

function defineEventHandler(emitter, name) {
// 8.1.5.1 Event handlers - basically `on[eventName]` attributes
let eventHandlerValue = undefined;
Object.defineProperty(emitter, `on${name}`, {
get() {
return eventHandlerValue;
},
set(value) {
if (eventHandlerValue) {
emitter.removeEventListener(name, eventHandlerValue);
}
if (typeof value === 'function') {
emitter.addEventListener(name, value);
}
eventHandlerValue = value;
}
});
}
module.exports = {
Event,
EventTarget,
NodeEventTarget,
defineEventHandler,
};
33 changes: 33 additions & 0 deletions test/parallel/test-eventtarget.js
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Expand Up @@ -6,6 +6,7 @@ const {
Event,
EventTarget,
NodeEventTarget,
defineEventHandler
} = require('internal/event_target');

const {
Expand Down Expand Up @@ -438,4 +439,36 @@ ok(EventTarget);
strictEqual(target.toString(), '[object EventTarget]');
const event = new Event('');
strictEqual(event.toString(), '[object Event]');
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{
const EventTarget();
defineEventHandler(target, 'foo');
target.onfoo = common.mustCall();
target.dispatchEvent(new Event('foo'));
}
{
const EventTarget();
defineEventHandler(target, 'foo');
let count = 0;
target.onfoo = () => count++;
target.onfoo = common.mustCall(() => count++);
target.dispatchEvent(new Event('foo'));
strictEqual(count, 1);
}
{
const EventTarget();
defineEventHandler(target, 'foo');
let count = 0;
target.addEventListener('foo', () => count++);
target.onfoo = common.mustCall(() => count++);
target.dispatchEvent(new Event('foo'));
strictEqual(count, 2);
}
{
const EventTarget();
defineEventHandler(target, 'foo');
let fn = common.mustNotCall(() => count++);
target.onfoo = fn;
strictEqual(target.onfoo, fn);
target.onfoo = null;
target.dispatchEvent(new Event('foo'));
}