Deep Omit Objects by Dot Key Paths

type PathTree = Map<string, PathTree>;

const FORBIDDEN_KEYS = new Set(["__proto__", "constructor", "prototype"]);

export function omitDeep<Value>(value: Value, paths: readonly string[]): Value {
  if (!Array.isArray(paths)) throw new TypeError("paths must be an array");
  if (paths.length === 0) return value;
  const tree: PathTree = new Map();
  for (const path of paths) {
    if (typeof path !== "string" || path.trim() === "") {
      throw new TypeError("paths must be non-empty strings");
    }
    const segments = path.split(".").map((segment) => segment.trim());
    if (segments.some((segment) => segment === "")) throw new Error(`invalid path "${path}"`);
    for (const segment of segments) {
      if (FORBIDDEN_KEYS.has(segment)) throw new Error(`path "${path}" contains a forbidden key`);
    }
    insert(tree, segments);
  }
  return clone(value, tree) as Value;
}

function insert(tree: PathTree, segments: readonly string[]): void {
  let node = tree;
  for (const segment of segments) {
    let child = node.get(segment);
    if (child === undefined) {
      child = new Map();
      node.set(segment, child);
    }
    node = child;
  }
}

function clone(value: unknown, tree: PathTree): unknown {
  if (Array.isArray(value)) {
    return value.map((item, index) => {
      const child = tree.get(String(index));
      if (child !== undefined && child.size === 0) return undefined;
      return clone(item, child ?? tree);
    });
  }
  if (value !== null && typeof value === "object") {
    const prototype = Object.getPrototypeOf(value);
    if (prototype !== Object.prototype && prototype !== null) {
      throw new TypeError("omitDeep only supports plain objects and arrays");
    }
    const output: Record<string, unknown> = {};
    for (const [key, item] of Object.entries(value as Record<string, unknown>)) {
      const child = tree.get(key);
      if (child !== undefined && child.size === 0) continue;
      output[key] = clone(item, child ?? new Map());
    }
    return output;
  }
  return value;
}

const source = {
  id: 1,
  password: "secret",
  profile: { email: "[email protected]", token: "abc", nested: { keep: true } },
  items: [{ id: 1, token: "a" }, { id: 2, token: "b" }],
};
const sanitized = omitDeep(source, ["password", "profile.token", "items.token"]);
console.log(JSON.stringify(sanitized));
console.log(JSON.stringify(source));