Function if_block

packages/svelte/src/internal/client/dom/blocks/if.js:21–72

(node, fn, elseif = false)

 * @returns {void}
 */
export function if_block(node, fn, elseif = false) {
	/** @type {TemplateNode | undefined} */
	var marker;
	if (hydrating) {
		marker = hydrate_node;
		hydrate_next();
	}

	var branches = new BranchManager(node);
	var flags = elseif ? EFFECT_TRANSPARENT : 0;

	/**
	 * @param {number | false} key
	 * @param {null | ((anchor: Node) => void)} fn
	 */
	function update_branch(key, fn) {
		if (hydrating) {
			var data = read_hydration_instruction(/** @type {TemplateNode} */ (marker));

			// "[n" = branch n, "[-1" = else
			if (key !== parseInt(data.substring(1))) {
				// Hydration mismatch: remove everything inside the anchor and start fresh.
				// This could happen with `{#if browser}...{/if}`, for example
				var anchor = skip_nodes();

				set_hydrate_node(anchor);
				branches.anchor = anchor;

				set_hydrating(false);
				branches.ensure(key, fn);
				set_hydrating(true);

				return;
			}
		}

		branches.ensure(key, fn);
	}

	block(() => {
		var has_branch = false;

		fn((fn, key = 0) => {
			has_branch = true;
			update_branch(key, fn);
		});

		if (!has_branch) {
			update_branch(-1, null);
		}
	}, flags);
}