tfg-event-context-plugin-node

event-context

• Event context for JavaScript
• Work in both NodeJS and browsers
• No dependencies

Features

• automatic state passing to downstream functions without explicitly declaring them in functions' parameters (think of React's context but with inheritance). State values are accessible everywhere with ctx.getState()
• automatic disposal for every pending tasks and event listeners to prevent memory leaks. EventContext works with Promise as well, so you can abort nested unresolved promises with ease. Context disposal is accessible everywhere with ctx.dispose()

event-context-plugin-node

Make EventContext package aware of jQuery bindings

Installation:

npm i -S tfg-event-context tfg-event-context-plugin-node

Usages

Passing data across functions without declaring them each time.

This is super useful to getting the request that causing an unexpected error. See the example below, it was not easy to get the req inside a downstream function without explicitly passing the req along the way.

import { withContext, getCurrentContext } from 'tfg-event-context';
import { patch } from 'tfg-event-context-plugin-node';

// patch all NodeJS binding after this call
patch();

const server = http.createServer(withContext((req, res) => {
  const ctx = getCurrentContext();
  const state = ctx.getState();

  state.req = req;

  handleRequest(req.path, (err, value) => {
    res.end(value);
  });
}));

function handleRequest(path, callback) {
  // do some works with path
  process.nextTick(() => {
    callDB(callback);
  });
}

function callDB(callback) {
  try {
    somethingWrong();
  } catch (ex) {
    const ctx = currentContext();
    const { req } = ctx.getState();
    const { method, url } = req;
    console.error('Server Error. Gracefully dying. Request causing error: ', method, url);
  }
}

Auto unbinding

When you decide to stop all event listeners created in an context, just call ctx.dispose()

const ctx = getCurrentContext();
ctx.dispose()

All bound event handlers within the context will be removed.

See also

EventContext for jQuery https://www.npmjs.com/package/tfg-event-context-plugin-jquery