accessing a getter from a parameterized getter

this can be undefined inside arrow function because it’s not interchangeable with regular function and gets a context from parent scope.

The usage of this and state is explained in details in the documentation. Either this or state can be used, but this has better Typescript and thus IDE support.

In the first snippet, state is already available in function scope, there is no need to access this:

multiSum: (state) => (count) => state.sum * count

In the second snippet, const store = this isn’t needed because a store is already this.

multiSum() {
  return (count) => this.sum * count
}