Optional chaining with JS Proxy

optional-chaining-proxy.js

const unwrapSymbol = Symbol();

function unwrap(x) {

    if (this == null)
        return this;
    
    let f = this[unwrapSymbol];
    
    if (typeof f !== "function")
        return this;
    
    return f.call(this);
}

const Nothing = new Proxy(Object.seal(function() {}), {

    get(target, key) { return key === unwrapSymbol ? (_=> void 0) : Nothing },
    set() {},
    has() { return true },
    apply() { return Nothing },
    construct() { return Nothing },
});

const maybeHandler = {

    get(target, key) { return key === unwrapSymbol ? (_=> target) : Maybe(target[key]) },
    has(target, key) { return key === unwrapSymbol || key in target },
    apply(target, thisArg, argumentList) { return Maybe(target.apply(thisArg, argumentList)) },
};

function Maybe(x) {

    return x === Nothing || x == null ? Nothing : new Proxy(Object(x), maybeHandler);
}

// alert(Maybe(self).document.scripts[0].parentNode.nodeName::unwrap());