batches() — svelte Function Reference

Source Code

packages/svelte/src/internal/client/reactivity/batch.js lines 373–450

	#commit() {
		// If there are other pending batches, they now need to be 'rebased' —
		// in other words, we re-run block/async effects with the newly
		// committed state, unless the batch in question has a more
		// recent value for a given source
		if (batches.size > 1) {
			this.previous.clear();

			var previous_batch_values = batch_values;
			var is_earlier = true;

			for (const batch of batches) {
				if (batch === this) {
					is_earlier = false;
					continue;
				}

				/** @type {Source[]} */
				const sources = [];

				for (const [source, value] of this.current) {
					if (batch.current.has(source)) {
						if (is_earlier && value !== batch.current.get(source)) {
							// bring the value up to date
							batch.current.set(source, value);
						} else {
							// same value or later batch has more recent value,
							// no need to re-run these effects
							continue;
						}
					}

					sources.push(source);
				}

				if (sources.length === 0) {
					continue;
				}

				// Re-run async/block effects that depend on distinct values changed in both batches
				const others = [...batch.current.keys()].filter((s) => !this.current.has(s));
				if (others.length > 0) {
					// Avoid running queued root effects on the wrong branch
					var prev_queued_root_effects = queued_root_effects;
					queued_root_effects = [];

					/** @type {Set<Value>} */
					const marked = new Set();
					/** @type {Map<Reaction, boolean>} */
					const checked = new Map();
					for (const source of sources) {
						mark_effects(source, others, marked, checked);
					}

					if (queued_root_effects.length > 0) {
						current_batch = batch;
						batch.apply();

						for (const root of queued_root_effects) {
							batch.#traverse_effect_tree(root, [], []);
						}

						// TODO do we need to do anything with the dummy effect arrays?

						batch.deactivate();
					}

					queued_root_effects = prev_queued_root_effects;
				}
			}

			current_batch = null;
			batch_values = previous_batch_values;
		}

		this.committed = true;
		batches.delete(this);
	}