- Event context for JavaScript
- Work in both NodeJS and browsers
- No dependencies
- 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()
EventContext for jQuery (jQuery events) https://www.npmjs.com/package/tfg-event-context-plugin-jquery
EventContext for NodeJS (nextTick, EventEmitter) https://www.npmjs.com/package/tfg-event-context-plugin-node
npm i -S tfg-event-context
# to use it with a plugin, just add the plugin package
npm i -S tfg-event-context-plugin-nodeThis 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);
}
}State values are prototypically inherited (think of angular1's scope).
// initiate contexts
const parent = createContext('parent');
const child = createContext('child');
const pState = parent.getState();
const cState = child.getState();
// state can be set even before running.
pState.parentOnly = 'parentOnly';
pState.shared = 'parentShared';
cState.childOnly = 'childOnly';
cState.shared = 'childOverwrite';
const childComputation = () => setTimeout(() => {
// child
const state = getCurrentContext().getState();
expect(state.childOnly).equal('childOnly');
expect(state.parentOnly).equal('parentOnly');
expect(state.shared).equal('childOverwrite');
done();
}, 10);
const parentComputaion = () => setTimeout(() => {
// parent
child.run(() => {
// child
childComputation()
})
}, 10)
parent.run(() => {
// parent
parentComputaion();
});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.
All contributions are super welcome
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