listen

Adds an event listener that is removed when the element is removed.

listen(type: string, handler: (event: Event) => unknown, target?: EventTarget): void
listen("keydown", onKey);
listen("resize", layout, window);
listen("visibilitychange", pause, document);

Parameters

Parameter Type Default Meaning
type string required Event name
handler (event) => unknown required Listener
target EventTarget host Where to listen

Same as target.addEventListener(type, handler, { signal }) with the element's signal. The return value of handler is ignored (use event.preventDefault() to cancel).

Example

Previewindex.htmlkey-display.html

Last key pressed anywhere: none

 
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>listen demo</title>
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@realmorg/realm@alpha/dist/realm.css">
  <script type="module" src="https://cdn.jsdelivr.net/npm/@realmorg/realm@alpha/dist/realm.js"></script>
</head>
<body>
  <import-element from="./key-display.html"></import-element>

  <key-display></key-display>
</body>
</html>
<custom-element name="key-display">
  <script>
    const keys = useState({ last: "" });

    listen("keydown", (event) => {
      keys.last = event.key;
    }, window);
  </script>

  <p>Last key pressed anywhere: <kbd><slot name="#keys.last">none</slot></kbd></p>
</custom-element>

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