Deep lens into an object

lens.ts

type NestedObj = {
    [x: string]: string | number | boolean | null | undefined | NestedObj;
};

const lens = (obj: NestedObj, path: string) => {
    const parts = path.split(".");
    const [lastPart] = parts.slice(-1);

    let current: NestedObj = obj;
    for (const part of parts) {
        const value = current[part];

        if (typeof value === "object" && value) {
            current = value;
        }

        if (part === lastPart || value === void 0) {
            return value;
        }
    }

    return;
};