Naïve approximation of Swift's nil-safe property access operator `?` - based on Zakas' "Defensive Objects", but kinder.

nil.js

import nil from  'optionil'

let obj = {
    str: 'literal',
    obj: {
        num: 5
    }
};

obj = nil(obj);
obj.str; // literal
obj.obj; // [object Object]
obj.obj.foo.bar.baz; // undefined (does not throw)

optionil.js

export default function optionil(target) {
    var value;

    value = target;
    if (target === undefined || target === null || target !== Object(target)) {
        target = {};
    }

    return new Proxy(target, {
        get: function (target, prop) {

            switch (prop) {
                case 'toString':
                    return function toString() {
                        if (value === undefined || value === null) {
                            return String(value);
                        }
                        return value.toString();
                    }

                case 'valueOf':
                    return function valueOf() {
                        if (value === undefined || value === null) {
                            return value;
                        }
                        return value.valueOf();
                    }
                default:
                    return optionil(target[prop]);
            }
        }
    });
}