nee

Nee is a porting of Node.JS EventEmitter class in ES2015. It's API is the same of the Node.JS's one (is based on the node v6 source code) and passes the same test suite used in node core

Why?

Building complex web applications probably involves creating custom events on custom objects. Node.JS EventEmitter is an extremely powerful event emitter library, but cannot be used in a browser context.

Nee allows you to use it while creating your JS client code, compiling it along with your ES6+ code.

How?

Install via bower

$ bower install --save nee

and extend the EventEmitter class in your code

import EventEmitter from "path/to/event-emitter";

class MyEmitter extends EventEmitter
{
    method() {
        let data = "event_data";
        this.emit('event_one', data);
    }
}

API

Static:

• EventEmitter.defaultMaxListeners - By default, a maximum of 10 listeners can be registered for any single event. This limit can be changed for individual EventEmitter instances using the emitter.setMaxListeners(n) method.

Methods:

• addListener(event, handler) - Alias for on(event, handler)
• emit(eventName[, arg1][, arg2][, ...]) - Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each. Returns true if the event had listeners, false otherwise.
• eventNames() - Returns an array listing the events for which the emitter has registered listeners
• getMaxListeners() - Returns the current max listener value for the emitter. Defaults to defaultMaxListeners
• listenerCount(eventName) - Returns the number of listeners listening to the event named eventName
• listeners(eventName) - Returns a copy of the array of listeners for the event named eventName
• on(eventName, listener) - Adds the listener function to the end of the listeners array for the event named eventName. Returns self, so that calls can be chained
• once(eventName, listener) - Adds a one time listener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.
• prependListener(eventName, listener) - Similar to on, but it adds the listener to the beginning of the listener array
• prependOnceListener(eventName, listener) - Adds a one time listener to be beginning of the listener array
• removeAllListeners([eventName]) - Removes all listeners, or those of the specified eventName
• removeListener(eventName, listener) - Removes listener from the listener array for the event named eventName
• setMaxListeners(n) - Set the max listener count after which the EventEmitter should raise a warning

Events:

• newListener(eventName, listener) - The EventEmitter instance will emit its own newListener event before a listener is added to its internal array of listeners
• removeListener(eventName, listener) - The removeListener event is emitted after the listener is removed

Error events

When an error occurs within an EventEmitter instance, the typical action is for an 'error' event to be emitted. These are treated as special cases.

If an EventEmitter does not have at least one listener registered for the 'error' event, and an 'error' event is emitted, the error is thrown.

const myEmitter = new MyEmitter();
myEmitter.emit('error', new Error('whoops!'));
// Throws

License

This project is released under the terms of the MIT license. See LICENSE file for more information

Contributions

Contributions, thoughts and ideas are always welcome

Thanks for reading, A