Prevent errors when calling WebMidi.disable() (issue #361)

djipco · Jun 3, 2023 · d300d50 · d300d50
1 parent 3bf6924
commit d300d50
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Showing 2 changed files with 8 additions and 3 deletions.
diff --git a/src/Output.js b/src/Output.js
@@ -71,7 +71,10 @@ export class Output extends EventEmitter {
     this.removeListener();
     this.channels.forEach(ch => ch.destroy());
     this.channels = [];
-    this._midiOutput.onstatechange = null;
+
+    // We check if it's still there because it could have theoretically be destroyed manually
+    if (this._midiOutput) this._midiOutput.onstatechange = null;
+
     await this.close();
     this._midiOutput = null;
   }

diff --git a/src/WebMidi.js b/src/WebMidi.js
@@ -424,11 +424,13 @@ class WebMidi extends EventEmitter {
    */
   async disable() {
 
+    // This needs to be done right away to prevent racing conditions in listeners while the inputs
+    // are being destroyed.
+    if (this.interface) this.interface.onstatechange = undefined;
+
     return this._destroyInputsAndOutputs().then(() => {
 
       if (navigator && typeof navigator.close === "function") navigator.close(); // jzz
-
-      if (this.interface) this.interface.onstatechange = undefined;
       this.interface = null; // also resets enabled, sysexEnabled
 
       /**