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. | | queue | no | action.type | string | Identifier that will be used to execute callbacks on separate queues |

Example Usage

Live Demo

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

const initialState = { count: 0 };

function reducer(state, action) {
  switch (action.type) {
    case "reset":
      return action.payload;
    case "increment":
      return { count: state.count + 1 };
    case "decrement":
      return { count: state.count - 1 };
    case "double-increment":
      return { count: state.count + 2 };
    case "double-decrement":
      return { count: state.count - 2 };
    default:
      return state;
  }
}

function App() {
  // Define your reducer the same way you would for React.useReducer()
  const [state, dispatch] = useOptimisticReducer(reducer, initialState);

  // optimistic actions
  const doubleIncAction = {
    type: "double-increment",
    optimistic: {
      callback: () => {
        return new Promise((resolve, reject) => {
          setTimeout(() => {
            console.log("This is a callback from double-increment");
            resolve();
          }, 3000);
        });
      },
      fallback: (prevState) => {
        alert("Failed!");
        dispatch({ type: "reset", payload: prevState });
      },
      queue: "double"
    }
  };

  const doubleDecAction = {
    type: "double-decrement",
    optimistic: {
      callback: () => {
        return new Promise(resolve => {
          setTimeout(() => {
            console.log("This is a callback from double-decrement");
            resolve();
          }, 3000);
        });
      },
      fallback: (prevState) => {
        alert("Failed!");
        dispatch({ type: "reset", payload: prevState });
      },
      queue: "double"
    }
  };

  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({ type: "decrement" })}>-</button>
      <button onClick={() => dispatch({ type: "increment" })}>+</button>
      <button onClick={() => dispatch(doubleIncAction)}>++</button>
      <button onClick={() => dispatch(doubleDecAction)}>--</button>
    </>
  );
}