redux-middleware-oneshot

0.1.1 verified Sat Apr 25 auth: no javascript

Creates a Redux middleware that invokes a setup function exactly once, when the first action passes through the middleware chain, allowing you to dispatch actions from arbitrary event sources (e.g., event emitters, WebSocket listeners) in a clean and timely manner. Current version 0.1.1 is early stage with limited releases and no tests. Redux peer dependency supports versions 1.x–3.x. Differentiates from other middleware patterns by ensuring one-time initialization tied to the first Redux action.

Common errors

error TypeError: createOneShot is not a function ↓

cause Using named import instead of default import: import { createOneShot } from 'redux-middleware-oneshot'

fix

Use default import: import createOneShot from 'redux-middleware-oneshot'

error Uncaught ReferenceError: dispatch is not defined ↓

cause Forgetting that the setup function receives dispatch as an argument and trying to use dispatch from outer scope

fix

Use the dispatch parameter provided to the callback: createOneShot(dispatch => { ... })

error The middleware does not dispatch any actions ↓

cause The setup function never runs because no initial action has been dispatched through the store

fix

Dispatch an initial dummy action to trigger the one-shot initialization: store.dispatch({ type: 'INIT' })

Warnings

gotcha The setup function only runs once, but only after the first action is dispatched. If no action is ever dispatched, the setup never initializes. ↓

fix Ensure at least one action is dispatched (e.g., an init action) to trigger the middleware initialization.

gotcha No tests exist in the package (as per README). Use with caution in production. ↓

fix Consider writing your own tests for the middleware behavior.

gotcha The package has low download counts and no recent updates. It may be considered unmaintained in terms of active development. ↓

fix Evaluate alternatives or contribute to the package if needed.

Install

npm install redux-middleware-oneshot

yarn add redux-middleware-oneshot

pnpm add redux-middleware-oneshot

Imports

default
wrong
```
const createOneShot = require('redux-middleware-oneshot');
```
correct
```
import createOneShot from 'redux-middleware-oneshot';
```
Package provides a default export and is ESM-compatible, though CJS require() may work depending on bundler.
createOneShot
wrong
```
import { createOneShot } from 'redux-middleware-oneshot';
```
correct
```
import createOneShot from 'redux-middleware-oneshot';
```
The function is exported as default, not as a named export. Using named import will result in undefined.

applyMiddleware usage

wrong

const store = applyMiddleware(createOneShot(...))(createStore)(reducer);

correct

import { applyMiddleware, createStore } from 'redux';
const middleware = createOneShot(dispatch => { ... });
const store = createStore(reducer, applyMiddleware(middleware));

Standard Redux middleware composition. Some developers mistakenly call createOneShot inside applyMiddleware inline incorrectly.

Quickstart

Demonstrates creating a one-shot middleware that listens to a custom event emitter and dispatches Redux actions from it.

import { createStore, applyMiddleware } from 'redux';
import createOneShot from 'redux-middleware-oneshot';

// Example reducer
const reducer = (state = [], action) => {
  if (action.type === 'ADD') {
    return [...state, action.payload];
  }
  return state;
};

// Create middleware that dispatches an action from a simulated event emitter
const emitter = {
  listeners: [],
  on(event, cb) { this.listeners.push(cb); },
  emit(event, data) { this.listeners.forEach(l => l(data)); }
};

const myMiddleware = createOneShot((dispatch) => {
  // This runs exactly once when first action goes through
  emitter.on('data', (value) => {
    dispatch({ type: 'ADD', payload: value });
  });
});

const store = createStore(reducer, applyMiddleware(myMiddleware));

// Trigger first action to initialize
store.dispatch({ type: '__INIT__' });

// Later, emit an event - it will be dispatched
emitter.emit('data', 42);
console.log(store.getState()); // [42]