Cancel pending transactions when calling destroy (#521)

* add jsdocs

* allow to pass more opts to socket

* allow to pass AbortSignal to socket

* add abort signal example

* lint the code

* remove vscode/ from gitignore

* drop node v14 (reached EOL April 2023)

* cancel pending transactions on destroy

* remove comments

Author: AndreMaz

index.js

@@ -637,6 +637,20 @@ class ModbusRTU extends EventEmitter {
         return false;
     }
 
+    /**
+     * Clears the timeout for all pending transactions.
+     * This essentially cancels all pending requests.
+     */
+    _cancelPendingTransactions() {
+        if (Object.keys(this._transactions).length > 0) {
+            Object.values(this._transactions).forEach((transaction) => {
+                if (transaction._timeoutHandle) {
+                    _cancelTimeout(transaction._timeoutHandle);
+                }
+            });
+        }
+    }
+
     /**
      * Close the serial port
      *
@@ -661,6 +675,9 @@ class ModbusRTU extends EventEmitter {
      *      or failure.
      */
     destroy(callback) {
+        // cancel all pending requests as we're closing the port
+        this._cancelPendingTransactions();
+
         // close the serial port if exist and it has a destroy function
         if (this._port && this._port.destroy) {
             this._port.removeAllListeners("data");