change order for listeners

Port of nodejs/node@d783fc5
browserify · Feb 27, 2021 · 0f82983 · 0f82983
1 parent 133faed
commit 0f82983
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Showing 2 changed files with 19 additions and 8 deletions.
diff --git a/events.js b/events.js
@@ -474,7 +474,13 @@ function addErrorHandlerIfEventEmitter(emitter, handler, flags) {
 }
 
 function eventTargetAgnosticAddListener(emitter, name, listener, flags) {
-  if (typeof emitter.addEventListener === 'function') {
+  if (typeof emitter.on === 'function') {
+    if (flags.once) {
+      emitter.once(name, listener);
+    } else {
+      emitter.on(name, listener);
+    }
+  } else if (typeof emitter.addEventListener === 'function') {
     // EventTarget does not have `error` event semantics like Node
     // EventEmitters, we do not listen for `error` events here.
     emitter.addEventListener(name, function wrapListener(arg) {
@@ -485,12 +491,6 @@ function eventTargetAgnosticAddListener(emitter, name, listener, flags) {
       }
       listener(arg);
     });
-  } else if (typeof emitter.on === 'function') {
-    if (flags.once) {
-      emitter.once(name, listener);
-    } else {
-      emitter.on(name, listener);
-    }
   } else {
     throw new TypeError('The "emitter" argument must be of type EventEmitter. Received type ' + typeof emitter);
   }

diff --git a/tests/events-once.js b/tests/events-once.js
@@ -170,12 +170,23 @@ function onceWithEventTargetError() {
   });
 }
 
+function prioritizesEventEmitter() {
+  var ee = new EventEmitter();
+  ee.addEventListener = assert.fail;
+  ee.removeAllListeners = assert.fail;
+  process.nextTick(function () {
+    ee.emit('foo');
+  });
+  return once(ee, 'foo');
+}
+
 module.exports = Promise.all([
   onceAnEvent(),
   onceAnEventWithTwoArgs(),
   catchesErrors(),
   stopListeningAfterCatchingError(),
   onceError(),
   onceWithEventTarget(),
-  onceWithEventTargetError()
+  onceWithEventTargetError(),
+  prioritizesEventEmitter()
 ]);