Function subscribe

src/createStore.ts:202–244

* Adds a change listener. It will be called any time an action is dispatched, * and some part of the state tree may potentially have changed. You may then * call `getState()` to read the current state tree inside the callback. * * You may call `dispatch()` from a change listener, with th

(listener: () => void)

   * @returns A function to remove this change listener.
   */
  function subscribe(listener: () => void) {
    if (typeof listener !== class="st">'function') {
      throw new Error(
        `Expected the listener to be a function. Instead, received: '${kindOf(
          listener
        )}'`
      )
    }

    if (isDispatching) {
      throw new Error(
        class="st">'You may not call store.subscribe() while the reducer is executing. ' +
          class="st">'If you would like to be notified after the store has been updated, subscribe from a ' +
          class="st">'component and invoke store.getState() in the callback to access the latest state. ' +
          class="st">'See https:class="cm">//redux.js.org/api/store#subscribelistener for more details.'
      )
    }

    let isSubscribed = true

    ensureCanMutateNextListeners()
    const listenerId = listenerIdCounter++
    nextListeners.set(listenerId, listener)

    return function unsubscribe() {
      if (!isSubscribed) {
        return
      }

      if (isDispatching) {
        throw new Error(
          class="st">'You may not unsubscribe from a store listener while the reducer is executing. ' +
            class="st">'See https:class="cm">//redux.js.org/api/store#subscribelistener for more details.'
        )
      }

      isSubscribed = false

      ensureCanMutateNextListeners()
      nextListeners.delete(listenerId)
      currentListeners = null
    }
  }

  /**
   * Dispatches an action. It is the only way to trigger a state change.