svelte/documentation/tutorial/12-actions/01-actions/app-b/click_outside.js

export function clickOutside(node) {
	const handleClick = (event) => {
		if (!node.contains(event.target)) {
			node.dispatchEvent(new CustomEvent('outclick'));
		}
	};

	document.addEventListener('click', handleClick, true);

	return {
		destroy() {
			document.removeEventListener('click', handleClick, true);
		}
	};
}