How to Use Redux with TypeScript
TypeScript can provide type-safety for reducers in your application, improves the documentation of your code, and overall improves long-term maintainability. Also, Redux officially recommends using static typing in their docs. Let's re-implement a todolist app. It is a basic example that many are familiar with, so it will be easier to focus on TypeScript part of a deal. Create a new React app using Create React App with the TypeScript template: First of all, we need to add dependencies to our app. We're going to need redux , react-redux, and types for the last one. We won't need an additional types package for Redux since it has its own type annotations. When it's done, we can create a state. Define types for the store state and todo items: Then, create a default value for the store: When the state is created, we can create actions that will change the state. To be short, we will have only 2 actions that will add a new todo or mark them complete or incomplete. When typings are completed, we create the actions themselves: Now we can add a reducer for todos: If we had more than one reducer we would want to combine them using the combineReducers function: It would allow us to create a single store instead of many for each feature. When everything is done, we can create a store: The react-redux package has a Provider component that lets you connect your components with the store. Finally, when everything is ready, we can use our actions in components. react-redux has a set of hooks that can access the store and dispatch actions. The useDispatch hook lets us fire actions: For accessing the state value, react-redux has a useSelector hook. It is best to use useSelector than useStore to avoid unnecessary re-renders. This is the basics of typing the react-redux application. There are additional tricks that allow you to throw errors when an unknown action has been fired or to make type-checking even stricter. But we will cover them in a different post later.