event_on.js

{
  on(eventname,callback){
        if(!eventname)return false;
        if(!(callback && callback.constructor===Function))return false;

        if(!this[eventname]){
            this[eventname]=[];
        } 

        if(!this[eventname].includes(callback) && Array.isArray(this[eventname]) && this.hasOwnProperty(eventname)){
            this[eventname].push(callback);
        } 

    }
}