Function each

packages/svelte/src/internal/client/dom/blocks/each.js:177–404

(node, flags, get_collection, get_key, render_fn, fallback_fn = null)

 * @returns {void}
 */
export function each(node, flags, get_collection, get_key, render_fn, fallback_fn = null) {
	var anchor = node;

	/** @type {Map<any, EachItem>} */
	var items = new Map();

	var is_controlled = (flags & EACH_IS_CONTROLLED) !== 0;

	if (is_controlled) {
		var parent_node = /** @type {Element} */ (node);

		anchor = hydrating
			? set_hydrate_node(get_first_child(parent_node))
			: parent_node.appendChild(create_text());
	}

	if (hydrating) {
		hydrate_next();
	}

	/** @type {Effect | null} */
	var fallback = null;

	// TODO: ideally we could use derived for runes mode but because of the ability
	// to use a store which can be mutated, we can't do that here as mutating a store
	// will still result in the collection array being the same from the store
	var each_array = derived_safe_equal(() => {
		var collection = get_collection();

		return /** @type {V[]} */ (
			is_array(collection) ? collection : collection == null ? [] : array_from(collection)
		);
	});

	if (DEV) {
		tag(each_array, '{#each ...}');
	}

	/** @type {V[]} */
	var array;

	/** @type {Map<Batch, Set<any>>} */
	var pending = new Map();

	var first_run = true;

	/**
	 * @param {Batch} batch
	 */
	function commit(batch) {
		if ((state.effect.f & DESTROYED) !== 0) {
			return;
		}

		state.pending.delete(batch);

		state.fallback = fallback;
		reconcile(state, array, anchor, flags, get_key);