I have tried to write eventEmitter class following explanation on these link

but when I wrote my own code

class EventEmitter {
    constructor(){
        this.listeners = {};
    }

    addListener(eventName , fn){
        this.listeners[eventName] = this.listeners[eventName] || [];
        this.listeners[eventName].push(fn) 
        return this ;
    }

    on(eventName , fn) {
        this.addListener(eventName , fn);
        return this ;
    }

    removeListener(eventName , fn){
        if(!this.listeners[eventName] || this.listeners[eventName].length === 0){
            return ;
        }
        const index = this.listeners[eventName].indexOf(fn);
        this.listeners[eventName].splice(index ,1);
    }

   off(eventName , fn) {
        this.removeListener(eventName, fn);
    }

    once(eventName , fn){
        this.listeners[eventName] = this.listeners[eventName] || [] ;
        const onceWrapper = (...args)=>{
            fn(...args) ;
            this.removeListener(eventName , onceWrapper) ;
        }
       this.listeners[eventName].push(onceWrapper);
       return this ;
    }

    

    emit(eventName ,...args){
        this.listeners[eventName].forEach(fn => {
            fn(...args);
        });
        return this ;
    }
}





const obj = new EventEmitter() ;

const c1 = () =>{
    console.log("Callback 1");
}
const c2 = () =>{
    console.log("Callback 2");
}
const c3 = (x) =>{
    console.log(`Callback ${x}`);
}



obj.once("foo" , c1);
obj.once("foo" , c2);
obj.once("foo" , c3);



obj.emit("foo" ,3)

the output was logged
Callback 1
Callback 3

not
Callback 1
Callback 2
Callback 3

I printed the listenes[“foo”].length before calling emit() and after was first 3 then 1 it acted like skipping c2 I do not know the reason which dose not make forEach loop on all items and I also tried to add more callbacks but also it dose not call all functions