Function handler

src/preact/component/iframe.js:128–138

(event)

    /** @param {MessageEvent} event */
    const handler = (event) => {
      const iframe = iframeRef.current;
      if (
        !iframe ||
        event.source != iframe.contentWindow ||
        !matchesMessagingOrigin(event.origin)
      ) {
        return;
      }
      messageHandler(event);
    };

    const {defaultView} = iframe.ownerDocument;
    defaultView?.addEventListener('message', handler);