keys#

Retrieves the own property keys of an obj object, supporting both string and symbol keys. Includes an optional predicate to filter keys based on their name and property descriptor.

Usage Scenarios#

• Object Inspection: Get all keys of an object for inspection or iteration.
• Property Filtering: Filter keys based on enumerability or other descriptor properties.
• Symbol Support: Access symbol properties alongside string keys.

Examples#

import { keys } from 'funtool';

const obj = {
  a: 1,
  b: 2,
  get c() { return 3; }
};
Object.defineProperty(obj, 'd', {
  value: 4,
  enumerable: false
});
const sym = Symbol('e');
obj[sym] = 5;

// Get only enumerable keys (default)
keys(obj); // ['a', 'b', 'c', Symbol(e)]

// Get all keys, including non-enumerable
keys(obj, () => true); // ['a', 'b', 'c', 'd', Symbol(e)]

// Get only non-enumerable keys
keys(obj, (key, desc) => !desc.enumerable); // ['d']

// Get only symbol keys
keys(obj, (key) => typeof key === 'symbol'); // [Symbol(e)]

Signature#

function keys<T extends object>(
  obj: T,
  predicate?: (key?: string | symbol, descriptor?: PropertyDescriptor) => boolean
): (keyof T)[]

Parameters#

• obj (T extends object): The object whose keys are to be retrieved.
• predicate ((key?: string | symbol, descriptor?: PropertyDescriptor) => boolean): Optional function to filter keys.

Returns#

• ((keyof T)[]): An array of the object's own keys filtered by the predicate.