voluptasmollitia/packages/util/src/obj.ts

Monorepo for the Firebase JavaScript SDK

/**
 * @license
 * Copyright 2017 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

export function contains<T extends object>(obj: T, key: string): boolean {
  return Object.prototype.hasOwnProperty.call(obj, key);
}

export function safeGet<T extends object, K extends keyof T>(
  obj: T,
  key: K
): T[K] | undefined {
  if (Object.prototype.hasOwnProperty.call(obj, key)) {
    return obj[key];
  } else {
    return undefined;
  }
}

export function isEmpty(obj: object): obj is {} {
  for (const key in obj) {
    if (Object.prototype.hasOwnProperty.call(obj, key)) {
      return false;
    }
  }
  return true;
}

export function map<K extends string, V, U>(
  obj: { [key in K]: V },
  fn: (value: V, key: K, obj: { [key in K]: V }) => U,
  contextObj?: unknown
): { [key in K]: U } {
  const res: Partial<{ [key in K]: U }> = {};
  for (const key in obj) {
    if (Object.prototype.hasOwnProperty.call(obj, key)) {
      res[key] = fn.call(contextObj, obj[key], key, obj);
    }
  }
  return res as { [key in K]: U };
}