object-fns/src/index.ts

Object utility functions

export type FilterCallback = (value: any, key: string, obj: object) => boolean;

export function map(
  obj: object,
  fn: (value: any, key: string, obj: object) => any,
): object {
  const result = {};
  for (const key in obj) {
    const value = fn(obj[key], key, obj);
    if (value !== undefined) {
      result[key] = value;
    }
  }
  return result;
}

export function filterBy(obj: object, keys: string[]): object {
  const result = {};
  for (const key of keys) {
    if (key in obj) {
      result[key] = obj[key];
    }
  }
  return result;
}

export function filter(obj: object, fn: FilterCallback): object {
  const result = {};
  for (const key in obj) {
    if (fn(obj[key], key, obj)) {
      result[key] = obj[key];
    }
  }
  return result;
}

export function findKey(obj: object, fn: FilterCallback): string {
  for (const key in obj) {
    if (fn(obj[key], key, obj)) {
      return key;
    }
  }
}

export function all(obj: object, fn: FilterCallback): boolean {
  for (const key in obj) {
    if (!fn(obj[key], key, obj)) {
      return false;
    }
  }
  return true;
}

export function reduce<T = any>(
  obj: object,
  fn: (prev: T, value: any, key: string, obj: object) => T,
  start: T,
): T {
  let result: T = start;
  for (const key in obj) {
    result = fn(result, obj[key], key, obj);
  }
  return result;
}