JS: No contents in array from parent class

I am using two classes in javascript.

class Challenge and class Modules, that extends Challenge.

in Challenge i have this constructor:

constructor() {
    this.handles = [];
}

and this method:

bla() {

    let elmnts = document.querySelectorAll("p"); // 5x
    
        for(let i=0; i < elmnts.length; i++) {
        
            let elmnt = elmnts[i];
            this.handles[elmnt['id']] = elmnt; // saves the handles to each element in separate array for later use
        
        }

}

in the child Class i am trying to use this “this.handles” array, but it is always empty.

It is not “undefined” but it is an empty array as i defined it in the constructor. its like the entries have never been set… but they are (as console.log() shows, when i insert it directly after the for()-loop)

console.log(this.handles); // --> []

Why does this happen?