I want to use the same variable in 2 javascript files modify it in both files and get the updated value to both files. I tried this. But it doesn't worked.

first.js

let marks = 0;

function func1() {
    function add() {
        marks = marks + 5;
        alert(marks);
        window.location.replace("second.html");
    }
    return {
        add:add;
    }
}

export default func1;

second.js

import func1 from '../first';
func1().add();

function func2() {
    function add2() {
        marks = marks + 5;
        alert(marks);
        window.location.replace("third.html");
    }
    return {
        add2:add2;
    }
}

export default func2;