value Class — svelte Architecture

Source Code

packages/svelte/types/index.d.ts lines 2596–2698

declare module 'svelte/store' {
	/** Callback to inform of a value updates. */
	export type Subscriber<T> = (value: T) => void;

	/** Unsubscribes from value updates. */
	export type Unsubscriber = () => void;

	/** Callback to update a value. */
	export type Updater<T> = (value: T) => T;

	/**
	 * Start and stop notification callbacks.
	 * This function is called when the first subscriber subscribes.
	 *
	 * @param set Function that sets the value of the store.
	 * @param update Function that sets the value of the store after passing the current value to the update function.
	 * @returns Optionally, a cleanup function that is called when the last remaining
	 * subscriber unsubscribes.
	 */
	export type StartStopNotifier<T> = (
		set: (value: T) => void,
		update: (fn: Updater<T>) => void
	) => void | (() => void);

	/** Readable interface for subscribing. */
	export interface Readable<T> {
		/**
		 * Subscribe on value changes.
		 * @param run subscription callback
		 * @param invalidate cleanup callback
		 */
		subscribe(this: void, run: Subscriber<T>, invalidate?: () => void): Unsubscriber;
	}

	/** Writable interface for both updating and subscribing. */
	export interface Writable<T> extends Readable<T> {
		/**
		 * Set value and inform subscribers.
		 * @param value to set
		 */
		set(this: void, value: T): void;

		/**
		 * Update value using callback and inform subscribers.
		 * @param updater callback
		 */
		update(this: void, updater: Updater<T>): void;
	}
	export function toStore<V>(get: () => V, set: (v: V) => void): Writable<V>;

	export function toStore<V>(get: () => V): Readable<V>;

	export function fromStore<V>(store: Writable<V>): {
		current: V;
	};

	export function fromStore<V>(store: Readable<V>): {
		readonly current: V;
	};
	/**
	 * Creates a `Readable` store that allows reading by subscription.
	 *
	 * @param value initial value
	 * */
	export function readable<T>(value?: T | undefined, start?: StartStopNotifier<T> | undefined): Readable<T>;
	/**
	 * Create a `Writable` store that allows both updating and reading by subscription.
	 *
	 * @param value initial value
	 * */
	export function writable<T>(value?: T | undefined, start?: StartStopNotifier<T> | undefined): Writable<T>;
	/**
	 * Derived value store by synchronizing one or more readable stores and
	 * applying an aggregation function over its input values.
	 *
	 * */
	export function derived<S extends Stores, T>(stores: S, fn: (values: StoresValues<S>, set: (value: T) => void, update: (fn: Updater<T>) => void) => Unsubscriber | void, initial_value?: T | undefined): Readable<T>;
	/**
	 * Derived value store by synchronizing one or more readable stores and
	 * applying an aggregation function over its input values.
	 *