mapStateToProps Redux

First argument passed in to the connect() function for a component.

• Selects the part of state that the component needs, and merges it into the components props.
• Called every time the store changes.
• Receives an argument of the entire store, returns an object of the data needed for the component.

For this example:

const TodoProps = {
    todos: Todo[];
}

const TodoList: React.FC<TodoProps> = ({ todos }) => {
    return {todos.map(TodoListItem)};
}

const mapStateToProps = (state) => {
    const { todos } = state;

    return { todos };
}

The TodoList component now receives todos as a prop.

See more details in the React Redux documentation