derived() — svelte Function Reference

Architecture documentation for the derived() function in index.js from the svelte codebase.

Function javascript ServerRuntime Serialization calls 1

Entity Profile

ServerRuntime→ Serialization→ derived() — svelte Function Reference

Dependency Diagram

graph TD
  e505bd51_6b0f_4df7_56da_6d6857e3c3d0["derived()"]
  1c4bc493_24af_177e_7307_a999997aceac["index.js"]
  e505bd51_6b0f_4df7_56da_6d6857e3c3d0 -->|defined in| 1c4bc493_24af_177e_7307_a999997aceac
  7f9b92d2_eded_1920_34ca_433cff036516["once()"]
  e505bd51_6b0f_4df7_56da_6d6857e3c3d0 -->|calls| 7f9b92d2_eded_1920_34ca_433cff036516
  style e505bd51_6b0f_4df7_56da_6d6857e3c3d0 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

packages/svelte/src/internal/server/index.js lines 476–490

export function derived(fn) {
	const get_value = once(fn);
	/**
	 * @type {T | undefined}
	 */
	let updated_value;

	return function (new_value) {
		if (arguments.length === 0) {
			return updated_value ?? get_value();
		}
		updated_value = new_value;
		return updated_value;
	};
}