Context API + useReducer() = Redux

Here is a gist of How we have found a substitute of redux i.e. by combining React Context API with useReducer() hook.

For the demonstration Follow the link .

What is Context API?

Context provides a technique which is unaccompanied by props at each level and which passes the data through the component tree.

In a stereotypical React application, data is passed from top to down (i.e. from parent to child) through props, but for certain types of props, this can be unmanageable (e.g. locale preference, UI theme) that many components need inside an application.

It lays out a path to share values like these amongst components without having to notably pass a prop through various levels of the tree.

When Context is actually used?

Global data for a tree (according to React components), is shared using context. For example: current authenticated user, theme, or preferred language.

With the help of context we can refrain from passing props in-between elements.

Suppose if a child of Component 1 changes something in its state [i.e. data], and that same data is in need by the child of Component 2 then it becomes hard to send data from one child to another[API hits will be costly if we are planning to do so.] Here what we do is, we manage Global Central storage so that the Child of Component 1 will update that Central store and the Child of Component 2 will become a subscriber of that Context Provider. It will update automatically through the provider.

Before Using Context

At different nesting levels, when many components needs to access a particular data, then context comes into play.

Amount of props that we need to pass through the application, which can be reduced by using the "inversion of control" and it thereby makes the code cleaner. This inturn gives more control to the root components. But when we direct towards more complexity higher in the tree then it makes those components even more complex and the lower level components becomes even more flexible.

NOTE: Redux, can also be used this problem but, we don't want to use a 3rd party package.

How we can Use Context API + Reducer to replace Redux

we are going to follow certain steps to implement it completely which are as follows.

• Firstly, we are going to create our data into store file which will have Global Data in Store folder (we can also set our initial state into this if any exists)

  const initialState = {
    contacts: [
      {
        id: "007",
        name: "Adhikansh Mittal",
        email: "[email protected]",
      },
      {
        id: "008",
        name: "Devandra Prajapat",
        email: "[email protected]",
      },
      {
        id: "009",
        name: "Vikas Agarwal",
        email: "[email protected]",
      },
    ],
    loading: false,
    error: null,
  };
  

• Now, we have to create our actions. It's an object which has all our functions which we are going to use. But It will not have their implementations here we will do it later in Provider.

  const actions = {
    DEL_CONTACT: "DEL_CONTACT",
    ADD_CONTACT: "ADD_CONTACT",
    START: "START",
    COMPLETE: "COMPLETE",
  };
  

• Now, we have to create our reducers. Reducer is a function which takes our state as well as our actions and on that basis, it returns the updated state..

  const reducer = (state, action) => {
    switch (action.type) {
      case actions.ADD_CONTACT:
        return {
          contacts: [...state.contacts, action.value],
        };
      case actions.DEL_CONTACT:
        return {
          contacts: state.contacts.filter(
            (contact) => contact.id !== action.value
          ),
        };
      case actions.START:
        return {
          loading: true,
        };
      case actions.COMPLETE:
        return {
          loading: false,
        };
      default:
        throw new Error();
    }
  };
  

• Now, we will create our Context. Creating a Context object will help when React renders a component that subscribes to this Context object it will read the current context value from the closest matching Provider above it in the tree.

  const ContactContext = React.createContext();
  

• Now, we create our Provider with the React Provider and payload the value here, which will be used to get all the changes to the consumer components which subscribes to that context. Plain and simple, it allows functional components to React access to reducer functions from your state management. A value prop is transferred to consuming components which are the successor to this Provider and are accepted by the Provider component. One Provider can be connected to many consumers. To overrule values thoroughly within the tree, providers are nested.

• Successors of a Providor, i.e. consumers, will re-render whenever the Provider’s value prop changes.

  The useEffect method is exempted from circulation to the successors of the Providor, i.e. consumers (including .contextType and useContext) .

  const ContactContextProvider = (props) => {
    const [state, dispatch] = React.useReducer(reducer, initialState);
  
    const value = {
      contacts: state.contacts,
      start: (value) => {
        dispatch({ type: actions.START, value });
      },
      complete: (value) => {
        dispatch({ type: actions.COMPLETE, value });
      },
      addContact: (value) => {
        dispatch({ type: actions.ADD_CONTACT, value });
      },
      delContact: (value) => {
        dispatch({ type: actions.DEL_CONTACT, value });
      },
    };
  
    return (
      <ContactContext.Provider value={value}>
        {props.children}
      </ContactContext.Provider>
    );
  };
  

  The same algorithm as Object.is is used to find out the changes by comparing the newer and the older values.

Contributing

Contributions are more than welcome! Please check out the contributing guide.

Thanks

Thank you for patient reading my writeup. It's been a wild ride while creating it.

If you like this repo, you should follow me on github and twitter

Shout out to Facebook Dev Team for the amazing Library.❤️