use-async-selector

Why

We had to do heavy calculations in our redux selectors and wanted to put them in a web worker. But useSelector() was not made for async stuff. That is why we needed a hook, that was able to handle async operations with access to the redux store. Now we can do all the heavy calculations within web workers.

Installation

npm i use-async-selector

Usage

import { useAsyncSelector } from "use-async-selector";

const myAsyncSelector = async state => fetch(`https://niceurl.com/${state.id}`);

const MyComponent = () => {
  const { loading, error, data } = useAsyncSelector(myAsyncSelector);

  // do stuff
  ...
}

Function Signature

useAsyncSelector(func: function): Object

Params

Param	Type	Description
func	function	Function, that needs to return a promise

Result

Property	Type	Description
loading	boolean	True, if promise is not resolved yet
error	boolean	True, if promise is rejected
data	null | mixed	Holds resolved data, if promised resolved.

Setup

To demonstrate its power, we are using the workerize-loader webpack plugin. But all other async stuff will work too.

1. Create a redux store

app.js

import { createStore } from "redux";

const defaultState = {
  items: [2, 3, 4, 5]
};

const reducer = (state = defaultState, action) => state;
const store = createStore(reducer);

const App = () => {
  return (
    <Provider store={store}>
      <MyComponent />
    </Provider>
  );
};

2. Create an async function

In our case, it is an exported worker function, that returns a promise.

worker.js

// put your heavy stuff here
export const selectItems = state => state.items.reverse();

3. Use the redux state within an async selector

my-component.js

import worker from "workerize-loader!./worker";
import { useAsyncSelector } from "use-asnyc-selector";

// create a worker instance
const instance = worker();

const MyComponent = () => {
  const { loading, error, data } = useAsyncSelector(instance.selectItems);

  if (loading || error) {
    return null;
  }

  // do stuff with the data
  console.log(data);
};

Examples

Web worker example