Flow control for your event emitters
Flow control for your event emitters.
EventEmitters are an important part of well-designed node.js applications.
emit() can get you pretty far, but wouldn't it be great if you
could run your event handlers asynchronously, with a continuation callback.
EventFlow adds the flow-controlly-goodness of async to your event emitters.
Attach eventflow to your event emitter:
var EventEmitter = require'events'EventEmitterrequire'eventflow'EventEmitteremitter = ;
Or, if you prefer not to extend the prototype:
var EventEmitter = require'events'EventEmitteremitter = ;require'eventflow'emitter;
Listen for some events, with or without continuation callbacks. EventFlow does some simple introspection of your listeners to see if they accept a callback or not.
emitteron'foo'// Do something synchronous;emitteron'foo'doSomethingAsynccallback;;;
Now use one of the flow control methods to invoke your handlers and respond when they are done.
emitterseries'foo'// The listeners ran in the order they were added and are all finished.;
emitterparallel'foo'// The listeners ran in parallel and are all finished.;
Event listeners with arguments
EventFlow supports calling your listeners with any number of arguments, as well as the optional continuation callback.
// In your logger or something:emitteron'purchase'console.logname + ' just bought ' + item + ' for ' + cost;// Somwhere else in your code:emitteron'purchase'saveToDBname: name item: item cost: cost callback;;// Perhaps in a form POST handler:emitterseries'purchase' 'Brian' 'T-Shirt' '$15.00'// The purchase was logged and saved to the db.;
EventFlow uses async directly to handle the flow-control, so you can use
results just like you already do.
// Synchronous listeners can return a result.emitteron'fruit'return 'apple';;// Async listeners use the standard (err, result) callback.emitteron'fruit'callbacknull 'orange';;emitterseries'fruit'console.logresults;// [ 'apple', 'orange' ];
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