A contrived example to demonstrate that you can listen for "/" as a shortcut key *and* still fall back to the native Quick Find, so your site does not completely commandeer a useful browser feature.

slash-search-fallback.html

<input type=search placeholder=search><br>
<textarea placeholder="won't respond to / shortcut"></textarea>
<script>
document.addEventListener(
	'keydown',
	(function() {
		let lastWasSlash = false,
			thisIsSlash,
			input = document.querySelector('input');
		return evt => {
			thisIsSlash = evt.key == '/' && !(
				evt.altKey
				|| evt.ctrlKey
				|| evt.isComposing
				|| evt.metaKey
				|| evt.shiftKey
			);
			if (thisIsSlash)
				switch (document.activeElement) {
					case document.body:
						evt.preventDefault();
						input.focus();
						break;
					case input:
						if (lastWasSlash && !input.value)
							input.blur();
						break;
					default:
						if (lastWasSlash)
							lastWasSlash = false;
						return;
				}
			lastWasSlash = thisIsSlash;
		};
	})(),
	{
		capture: true
	}
);
</script>