Using `this` within arrow function expressions within class methods can point to wrong `this`

// engine.* methods are from C++. snippet below replicates its behavior in a NodeJS environment
let engine = {};
engine.beginTimer = function(delay, func, oneshot) {
    if (oneshot) {
        setTimeout(func, delay);
    } else {
        setInterval(func, delay);
    }
}


var globalThis = this;

class Foo {
    constructor() {
        (() => {
            console.debug(this instanceof Foo); // true (QJSEngine & NodeJS)
            if (true) {
                console.debug(this); // undefined (QJSEngine); "Foo { prop: 'prop' }" (NodeJS)
            }
        })();
        engine.beginTimer(100, () => {
            console.debug(this instanceof Foo);  // true (QJSEngine & NodeJS)
            if (true) {
                console.debug(this.globalThis === this); // true (QJSEngine); false (NodeJS)
            }
        }, true);
    }
}