store

@iadvize/store

A lightweight Javascript store library.

📖 Documentation

Basic example

type Todo = {
  done: boolean;
  label: string;
};

type State = Todo[];

// initialise the store with an initial state
const todoStore = Store.create<State>(() => [
  { done: false, label: "writtings some doc" },
  { done: true, label: "napping" },
])();

// create a reducer function adding a new Todo
function appendNewTodoOnState(newTodo: string) {
  return function appendNewTodoReducer(state: State) {
    return [
      ...state,
      { done: false, label: newTodo }
    ];
  }
}

// associating the reducer function and a store instance
const appendNewTodo = Store.liftAndApply(appendNewTodoOnState, todoStore);

// create a reducer function removing all todos, ie. returning and empty state
const emptyTodosReducer = () => [];

// associating the reducer function and a store instance
const emptyTodos = todoStore.apply(emptyTodosReducer);

// registering a listener
const subscribeToTodoStore = todoStore.subscribe(newState => {
  console.log("newState", newState);
});

// applying the listener
const unsubscribeFromTodoStore = subscribeToTodoStore();

// triggering a change
appendNewTodo("have drink with my colleagues")();

// will log:
// newState, [{done: false, label: 'writtings some doc'},{done: true, label: 'napping'},{done: false, label: 'have drink with my colleagues'}]

// emptying the store 
emptyTodos();

// will log:
// newState, []

// removing the listener we don't need anymore
unsubscribeFromTodoStore();

Reference

Store.create - Store creation

Store.create<State>(initialState: () => State): () => Store<State>

You create a store with Store.create by passing it a function that will return your initial state. This will return you a function to call to create the corresponding store as many times you need.

Params

• initialState: () => State - Function that return the initial state

Returns

() => Store<State> - Effect to call to receive a Store initialized with the initial state

Example

const createTodoStore = Store.create<State>(() => [
  { done: false, label: "writtings some doc" },
  { done: true, label: "napping" }
]);

const todoStore = createTodoStore();

<store>.read - Reading the state

Call <store>.read to read the state.

<store>.read(): State

Returns

State - Returns the state.

Example

const state = store.read();
console.log('state', state);

<store>.subscribe - Subscribing to state change

You subscribe to state changes with <store>.subscribe. It accepts a listener that receives the new state as a parameter.

<store>.subscribe(listener: Listener<State>): () => Unsubscribe

Params

• listener: Listener<State> - Where Listener<State> = (state: State) => void. The function that will be called when state change with the new state as argument.

Returns

() => Unsubscribe - A function to call to apply the subscription as many times you need.

When applying a subscription, you will receive in return an unsubscribe function to call to unsubscribe this specific applied subscription where type Unsubscribe: () => void.

Example

// prepare the subscription to change
// subscribeToTodoStore :: () => Unsubscribe
const subscribeToTodoStore = todoStore.subscribe((state) =>
  console.log('new state', state);
);

// starting the listener
// unsubscribeFromTodoStore :: () => void 
const unsubscribeFromTodoStore = subscribeToTodoStore();

// unsubscribe when you are done
unsubscribeFromTodoStore();

<store>.apply - Updating state

Call <store>.apply with a reducer to update the store.

<store>.apply(reducer: (state: State) => State): () => void

Params

• reducer: (state: State) => State - A function that receive a state and return a new state.

Returns

() => void - An effect to call to apply the update synchronously.

Example

// preparing an update function
// appendNewTodoOnState :: (newTodo: string) => (state: State) => State
function appendNewTodoOnState(newTodo: string) {
  function appendNewTodoReducer(state: State) {
    return [
      ...state,
      { done: false, label: newTodo }
    ]
  }
}

// Preparing the update on the store
const appendNewTodo = todoStore.apply(
  appendNewTodoOnState('have drink with my colleagues')
);

// Applying the transformation
appendNewTodo();

Here we apply a reducer function directly on the store instance and trigger the change with the appendNewTodo function.

Of course we would need appendNewTodo to accept any todo rather than a preset one:

// Preparing the update on the store
// appendNewTodo :: (newTodo: string) => () => void
const appendNewTodo = (newTodo: string) => todoStore.apply(
  appendNewTodoOnState(newTodo)
);

// Applying the transformation
appendNewTodo('have drink with my colleagues')();

Because this operation is so common, we can use Store.liftAndApply which will handle the parameter passing for us and cut on the boilerplate:

// appendNewTodo :: (newTodo: string) => () => void
const appendNewTodo = Store.liftAndApply(appendNewTodoOnState, todoStore);

appendNewTodo('have drink with my colleagues')();

Store.liftAndApply - create a parametrized update

Call Store.liftAndApply to easily create an update effect function. Pass it a function that given any parameters returns a reducer State => State and the store.

Store.liftAndApply<
  State,
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  Fn extends (...args: any[]) => Reducer<State>
>(fn: Fn, store: Store<State>): (...args: Parameters<Fn>) => () => void

Params

• fn: Fn - Where Fn extends (...args: any[]) => Reducer<State> a function that returns a reducer.

• store: Store<State> - The store we want to update.

Returns

An function that accept fn arguments and return an effect to call to apply the update synchronously.

Example

// appendNewTodoOnState :: (newTodo: string, done: boolean) => (state: State) => State
function appendNewTodoOnState(newTodo: string, done: boolean) {
  function appendNewTodoReducer(state: State) {
    return [
      ...state,
      { done, label: newTodo }
    ]
  }
}

// appendNewTodo :: (newTodo: string, done: boolean) => () => void
const appendNewTodo = Store.liftAndApply(appendNewTodo, todoStore);

appendNewTodo('Groceries already done', true);