property_lookup.js

let sourceObject = { foo: { bar: { baz: { qux: { value: "Hit!" } } } } };
sourceObject.foo[Symbol.for('symbol')] = 'symbol value';

function lookup(object, path) {
    path = Array.isArray(path) ? path : path.split('.');

    for(let i = 0; i < path.length; i++) {
        object = object[path[i]];

        if (!object) break;
    }

    return object;
}

console.log('good arr:', lookup(sourceObject, ['foo', Symbol.for('symbol')]));
console.log('good str:', lookup(sourceObject, "foo.bar.baz.qux") );
console.log('bad str:', lookup(sourceObject, "foo.bar.baz.FAIL") );
console.log('bad str:', lookup(sourceObject, "foo.bar.FAIL.qux") );
console.log('bad str:', lookup(sourceObject, "FAIL.bar.baz.qux") );

Mmmm. Rev 1 of this version uses recursion, but I'm not sure I want to incur the cost of additional function calls. Ideally I'd like to be able to use this method in critical path logic.