signal

Holds a value and notifies subscribers when it changes.

interface Signal<T> {
  // Get or set the value
  (value?: T): T;
  // Set the value
  set: (value: T) => void;
  // Subscribe to changes
  subscribe: (fn: () => void) => () => void
  // Unsubscribe from changes
  unsubscribe: (fn: () => void) => void
  // Cleanup all subscribers
  cleanup: () => void;
}

/**
 * @param initialValue The initial value for the signal
 * @returns A signal function with methods
 */
signal<T>(initialValue: T): Signal<T>

Usage

Get

Get a signal by calling it with no arguments.

import { signal } from '@hellajs/core';

// Create a signal with an initial value
const count = signal(5);

// Read the current value
console.log(count()); // 5

Set

Update a signal value using the set method, or by calling it with a new value.

// Update using set method
count.set(10);
console.log(count()); // 10

// Update using function call
count(20);
console.log(count()); // 10

Subscribe

Subscribe to signals (or use effect) to get notified when the value changes.

// Subscribe to changes
const unsubscribe = count.subscribe(() => {
  console.log('Count changed:', count());
});

// Stop listening for changes
unsubscribe();

or similar to an eventListener:

const subscribeFn = () => {
  console.log('Count changed:', count());
}

// Subscribe to changes
count.subscribe(subscribeFn);

// Stop listening for changes
count.unsubscribe(subscribeFn);

Cleanup

Call cleanup when the signal is no longer needed. It will remove all subscribers and stop notifying them. Cleanup is required for global signals only. Signals created inside a component function are automatically cleaned when the component is unmounted.

count.cleanup();