Simple Custom Event Mixin

events.js

function EventMixin(Target){
    var listeners = {};
    var methods = {
        
        emit : function(ev){
            if( !listeners[ev] ) return;
            var ar = listeners[ev];
            var args = [].slice.call(arguments, 1);
            for(var i=0; i<ar.length; i++) ar[i].apply(this, args);
        },
        
        on : function(ev, fn){
            if( !listeners[ev] ) listeners[ev] = [];
            var ar = listeners[ev];
            for(var i=0; i<ar.length; i++) if( ar[i] == fn ) return;
            listeners[ev].push(fn);
        },
        
        un : function(ev, fn){
            if( !listeners[ev] ) return;
            var ar = listeners[ev];
            for(var i=0; i<ar.length; i++) if( ar[i] == fn ){
                ar.splice(i,1);
                return;
            }
        }
        
    };
    
    for(var name in methods)
        if( methods.hasOwnProperty(name) )
            Target.prototype[name] = methods[name];
    
};