fix: prevent nodeData.onHandlers overwrite

src/htmx.js

@@ -1950,7 +1950,9 @@ return (function () {
 
         function addHxOnEventHandler(elt, eventName, code) {
             var nodeData = getInternalData(elt);
-            nodeData.onHandlers = [];
+            if (!Array.isArray(nodeData.onHandlers)) {
+                nodeData.onHandlers = [];
+            }
             var func;
             var listener = function (e) {
                 return maybeEval(elt, function() {

test/attributes/hx-on-wildcard.js

@@ -175,4 +175,22 @@ describe("hx-on:* attribute", function() {
         delete window.foo;
         delete window.bar;
     });
+
+    it("cleans up all handlers when the DOM updates", function () {
+        // setup
+        window.foo = 0;
+        window.bar = 0;
+        var div = make("<div hx-on:increment-foo='window.foo++' hx-on:increment-bar='window.bar++'>Foo</div>");
+        make("<div>Another Div</div>"); // sole purpose is to update the DOM
+
+        // check there is just one handler against each event
+        htmx.trigger(div, "increment-foo");
+        htmx.trigger(div, "increment-bar");        
+        window.foo.should.equal(1);
+        window.bar.should.equal(1);
+
+        // teardown
+        delete window.foo;
+        delete window.bar;
+    });
 });

test/attributes/hx-on.js

@@ -171,4 +171,22 @@ describe("hx-on attribute", function() {
         delete window.foo;
         delete window.bar;
     });
+
+    it("cleans up all handlers when the DOM updates", function () {
+        // setup
+        window.foo = 0;
+        window.bar = 0;
+        var div = make("<div hx-on='increment-foo: window.foo++\nincrement-bar: window.bar++'>Foo</div>");
+        make("<div>Another Div</div>"); // sole purpose is to update the DOM
+
+        // check there is just one handler against each event
+        htmx.trigger(div, "increment-foo");
+        htmx.trigger(div, "increment-bar");        
+        window.foo.should.equal(1);
+        window.bar.should.equal(1);
+
+        // teardown
+        delete window.foo;
+        delete window.bar;
+    });
 });