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events: set default handler value #41970

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Merged
nodejs-github-bot merged 1 commit into from
Feb 16, 2022
Merged

events: set default handler value #41970

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events: set default handler value 
Event handler like BroadcastChannel.onmessage and AbortSignal.onabort
have a default value of `null` but we return `undefined`.

Return `null` and add a test.
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@benjamingr
benjamingr committed Feb 14, 2022
commit a70e891b003367b4c9adbde822c35be271afb441
2 changes: 1 addition & 1 deletion lib/internal/event_target.js
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Original file line number Diff line number Diff line change
Expand Up @@ -929,7 +929,7 @@ function defineEventHandler(emitter, name) {
// 8.1.5.1 Event handlers - basically `on[eventName]` attributes
ObjectDefineProperty(emitter, `on${name}`, {
get() {
return this[kHandlers]?.get(name)?.handler;
return this[kHandlers]?.get(name)?.handler ?? null;
},
set(value) {
if (!this[kHandlers]) {
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11 changes: 9 additions & 2 deletions test/parallel/test-eventtarget.js
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Original file line number Diff line number Diff line change
Expand Up @@ -408,6 +408,13 @@ let asyncTest = Promise.resolve();
target.onfoo = common.mustCall();
target.dispatchEvent(new Event('foo'));
}

{
const target = new EventTarget();
defineEventHandler(target, 'foo');
strictEqual(target.onfoo, null);
}

{
const target = new EventTarget();
defineEventHandler(target, 'foo');
Expand Down Expand Up @@ -623,14 +630,14 @@ let asyncTest = Promise.resolve();
strictEqual(et.constructor.name, 'EventTarget');
}
{
// Weak event handlers work
// Weak event listeners work
const et = new EventTarget();
const listener = common.mustCall();
et.addEventListener('foo', listener, { [kWeakHandler]: et });
et.dispatchEvent(new Event('foo'));
}
{
// Weak event handlers can be removed and weakness is not part of the key
// Weak event listeners can be removed and weakness is not part of the key
const et = new EventTarget();
const listener = common.mustNotCall();
et.addEventListener('foo', listener, { [kWeakHandler]: et });
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