How to recover/pass event Object between functions in JavaScript

I’m trying to understand how the “event” object is passed and recovered between functions. It was my understanding that event is passed by default as an argument and after seeing the example below it’s confusing me even more how this works. How “…args” is getting the event object?

const MyInput = document.querySelector('input');

const checkActivity=(f1)=>{
    return (...args)=>{
        console.log(args);
        f1(args);
    };
}

const MyFunc=(e)=>{
    console.log(e);
};

MyInput.addEventListener('input',checkActivity(MyFunc));

Answer

Here, checkActivity(MyFunc) is being executed before adding the event listener and not used as a callback. It’s the result of this call that is used as a callback. Callback that accepts (…args) possibly an event.