// class inheritence
class MyClass extends EvEmitter {}

// mixin prototype
Object.assign( MyClass.prototype, EvEmitter.prototype );

// single instance
let emitter = new EvEmitter();

emitter.on( eventName, listener )

emitter.off( eventName, listener )

emitter.once( eventName, listener )

emitter.emitEvent( eventName, args )

emitter.allOff()

// create event emitter
var emitter = new EvEmitter();

// listeners
function hey( a, b, c ) {
  console.log( 'Hey', a, b, c )
}

function ho( a, b, c ) {
  console.log( 'Ho', a, b, c )
}

function letsGo( a, b, c ) {
  console.log( 'Lets go', a, b, c )
}

// bind listeners
emitter.on( 'rock', hey )
emitter.on( 'rock', ho )
// trigger letsGo once
emitter.once( 'rock', letsGo )

// emit event
emitter.emitEvent( 'rock', [ 1, 2, 3 ] )
// => 'Hey', 1, 2, 3
// => 'Ho', 1, 2, 3
// => 'Lets go', 1, 2, 3

// unbind
emitter.off( 'rock', ho )

emitter.emitEvent( 'rock', [ 4, 5, 6 ] )
// => 'Hey' 4, 5, 6