Update listenOnce.md

Use `{ once: true }` as `options` to make the listener run at most one time.

snippets/listenOnce.md

@@ -1,26 +1,19 @@
 ---
 title: listenOnce
-tags: browser,event,closure,intermediate
+tags: browser,event,beginner
 ---
 
 Adds an event listener to an element that will only run the callback the first time the event is triggered.
 
-Use `EventTarget.addEventListener()` to add an event listener to an element, storing the reference in a variable.
-Use  a condition to call `fn` only the first time the listener is triggered. 
+Use `EventTarget.addEventListener()` to add an event listener to an element, using `{ once: true }` as options to only run the given callback once.
 
 ```js
-const listenOnce = (el, evt, fn) => {
-  let fired = false;
-  el.addEventListener(evt, (e) => {
-    if (!fired) fn(e);
-    fired = true;
-  });
-};
+const listenOnce = (el, evt, fn) => el.addEventListener(evt, fn, { once: true });
 ```
 
 ```js
 listenOnce(
-  document.getElementById('my-id),
+  document.getElementById('my-id'),
   'click',
   () => console.log('Hello world')
 ); // 'Hello world' will only be logged on the first click