properly call willunmount and destroy hooks

web/static/src/ts/widgets/clock.ts

@@ -6,6 +6,8 @@ const template = `<div class="o_clock"><t t-esc="state.currentTime"/></div>`;
 export class Clock extends Widget<Env> {
   name = "clock";
   template = template;
+  interval: any | undefined;
+
   state = {
     currentTime: ""
   };
@@ -15,9 +17,12 @@ export class Clock extends Widget<Env> {
   }
 
   mounted() {
-    setInterval(this.updateTime.bind(this), 500);
+    this.interval = setInterval(this.updateTime.bind(this), 500);
   }
 
+  willUnmount() {
+    clearInterval(this.interval);
+  }
   updateTime() {
     this.updateState({
       currentTime: new Date().toLocaleTimeString()