Function key

packages/svelte/src/internal/client/dom/blocks/key.js:16–40

(node, get_key, render_fn)

 * @returns {void}
 */
export function key(node, get_key, render_fn) {
	if (hydrating) {
		hydrate_next();
	}

	var branches = new BranchManager(node);

	var legacy = !is_runes();

	block(() => {
		var key = get_key();

		// NaN !== NaN, hence we do this workaround to not trigger remounts unnecessarily
		if (key !== key) {
			key = /** @type {any} */ (NAN);
		}

		// key blocks in Svelte <5 had stupid semantics
		if (legacy && key !== null && typeof key === 'object') {
			key = /** @type {V} */ ({});
		}

		branches.ensure(key, render_fn);
	});
}