Function createSignal

packages/core/primitives/signals/src/signal.ts:53–73

(
  initialValue: T,
  equal?: ValueEqualityFn<T>,
)

 * Creates a `Signal` getter, setter, and updater function.
 */
export function createSignal<T>(
  initialValue: T,
  equal?: ValueEqualityFn<T>,
): [SignalGetter<T>, SignalSetter<T>, SignalUpdater<T>] {
  const node: SignalNode<T> = Object.create(SIGNAL_NODE);
  node.value = initialValue;
  if (equal !== undefined) {
    node.equal = equal;
  }
  const getter = (() => signalGetFn(node)) as SignalGetter<T>;
  (getter as any)[SIGNAL] = node;
  if (typeof ngDevMode !== 'undefined' && ngDevMode) {
    getter.toString = () =>
      `[Signal${node.debugName ? ' (' + node.debugName + ')' : ''}: ${String(node.value)}]`;
  }

  runPostProducerCreatedFn(node);
  const set = (newValue: T) => signalSetFn(node, newValue);
  const update = (updateFn: (value: T) => T) => signalUpdateFn(node, updateFn);
  return [getter, set, update];
}

export function setPostSignalSetFn(fn: ReactiveHookFn | null): ReactiveHookFn | null {
  const prev = postSignalSetFn;