use-optimistic-reducer

React reducer hook for handling optimistic UI updates and race-conditions.

Installation

With npm:

$ npm install use-optimistic-reducer

With yarn:

$ yarn add use-optimistic-reducer

How It Works

Internally, useOptimisticReducer uses the React.useReducer() hook to handle its state. You can use useOptimisticReducer to update the state by dispatching an action.

Whenever you need to make an optimistic UI update, you simply need to add another property named as optimistic inside your action object.

By default, a queue is formed whenever a new action is being dispatched. If an action of the same type is dispatched, this action's callback will be put into the queue and wait until all the previous callbacks to be executed.

If you wish to put your callbacks onto a separate queue, you may define a string as the identifier for the queue.

An example of an optimistic action object would look like this:

const action = {
  type: "ADD_TODO",
  payload: {},
  optimistic: {
    callback: async () => {},
    fallback: (prevState) => {}, // (Optional)
    queue: "" // (Optional)
  }
}

The optimistic property

Name	Required	Default	Type	Description
callback	yes		Function	Callback function that will be called in the background. It should be an asynchronous function.
fallback	no		Function(prevState)	Fallback function that will be called when callback throws an error. prevState is the previous state before the error occurred, and it has the same type as the reducer state.
queue	no	action.type	string	Identifier that will be used to execute callbacks on separate queues

Example Usage

Demo with Typescript

import React from "react";
import useOptimisticReducer from "use-optimistic-reducer";

type StateProps = {
  reaction: string;
};

type Action =
  | { type: "SET_REACTION"; payload: string }
  | { type: "RESET_STATE"; payload: StateProps };

const reducer = (state: StateProps, action: Action) => {
  switch (action.type) {
    case "SET_REACTION":
      if (action.payload === state.reaction) {
        return { ...state, reaction: "" };
      }
      return { ...state, reaction: action.payload };
    case "RESET_STATE":
      return action.payload;
    default:
      return state;
  }
};

const apiCall = () => {
  return new Promise((res, rej) => {
    setTimeout(() => {
      console.log("Response from server");
      res();

      // reject promise to see execution of the fallback
      // rej();
    }, 1000);
  });
};

export default function App() {
  const [state, dispatch] = useOptimisticReducer(reducer, { reaction: "" });

  function handleClick(reaction: string) {
    dispatch({
      type: "SET_REACTION",
      payload: reaction,
      optimistic: {
        callback: apiCall,
        fallback: (prevState) => {
          // revert previous state in case the apiCall throws an exception
          dispatch({ type: "RESET_STATE", payload: prevState });
        },
        queue: "reaction"
      }
    });
  }

  return (
    <div>
      <h1>Reaction: {state.reaction.length ? state.reaction : "None"}</h1>
      <div>
        <button onClick={() => handleClick("Funny")}>
          <span role="img" aria-label="funny">
            😂
          </span>
          Funny
        </button>
        <button onClick={() => handleClick("Amazing")}>
          <span role="img" aria-label="amazing">
            😮
          </span>{" "}
          Amazing
        </button>
        <button onClick={() => handleClick("Sad")}>
          <span role="img" aria-label="sad">
            😢
          </span>{" "}
          Sad
        </button>
      </div>
    </div>
  );
}