Optional chaining with JS Proxy

optional-chaining-proxy.js

const unwrapSymbol = Symbol();

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

    get() { return Nothing },
    set() {},
    has() { return true },
    apply() { return Nothing },
    construct() { return Nothing },
});

const maybeHandler = {

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

function Maybe(x) {

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

Maybe.unwrap = function(x) {

    let val = x[unwrapSymbol];
    return val === x ? void 0 : val;
};