villers/HTML5_Gaming

Im working on a phaser 3 game and what i want to do is have a central file that defines all my variable and preload all my images that arent being defined ive tried so many thing ive probably over looked a lot of options, also i want it to be a class kinda like this

export default class preload extends Phaser.Scene {

    constructor() {
        super({key:'preload'});
    }
//define variable here
const windowWidth = window.innerWidth;
const widnowHeight = window.innerHeight;

    preload(){

       }
}

So can anyone help?