Class BranchManager

packages/svelte/src/internal/client/dom/blocks/branches.js:22–238

 * @template Key
 */
export class BranchManager {
	/** @type {TemplateNode} */
	anchor;

	/** @type {Map<Batch, Key>} */
	#batches = new Map();

	/**
	 * Map of keys to effects that are currently rendered in the DOM.
	 * These effects are visible and actively part of the document tree.
	 * Example:
	 * ```
	 * {#if condition}
	 * 	foo
	 * {:else}
	 * 	bar
	 * {/if}
	 * ```
	 * Can result in the entries `true->Effect` and `false->Effect`
	 * @type {Map<Key, Effect>}
	 */
	#onscreen = new Map();

	/**
	 * Similar to #onscreen with respect to the keys, but contains branches that are not yet
	 * in the DOM, because their insertion is deferred.
	 * @type {Map<Key, Branch>}
	 */
	#offscreen = new Map();

	/**
	 * Keys of effects that are currently outroing
	 * @type {Set<Key>}
	 */
	#outroing = new Set();

	/**
	 * Whether to pause (i.e. outro) on change, or destroy immediately.
	 * This is necessary for `<svelte:element>`
	 */
	#transition = true;

	/**
	 * @param {TemplateNode} anchor
	 * @param {boolean} transition
	 */
	constructor(anchor, transition = true) {
		this.anchor = anchor;
		this.#transition = transition;
	}

	/**
	 * @param {Batch} batch
	 */
	#commit = (batch) => {
		// if this batch was made obsolete, bail
		if (!this.#batches.has(batch)) return;