empty object - nberlette/is GitHub Wiki

@nick/is/empty-object

isEmptyObject

Signature

function isEmptyObject(it: unknown): it is EmptyObject;

Check if a value is an empty object.

Parameters
Name Info
value The value to check.
Returns

true if the value is an empty object, or false otherwise.

Category

Objects

Examples

import { isEmptyObject } from "jsr:@nick/is/empty-object";

console.log(isEmptyObject({})); // true
console.log(isEmptyObject(new Object())); // true

console.log(isEmptyObject({ a: 1 })); // false
console.log(isEmptyObject({ a: 1, b: 2 })); // false
console.log(isEmptyObject([])); // false
console.log(isEmptyObject(null)); // false
console.log(isEmptyObject(undefined)); // false
console.log(isEmptyObject(1)); // false

EmptyObject

Signature

export type EmptyObject = {
  [_ in undefined]?: never;
};

Represents an empty object with no own properties.

Category

Objects

Examples

import type { EmptyObject } from "jsr:@nick/is/empty-object";

const foo: EmptyObject = {}; // OK
const bar: EmptyObject = []; // ts(6133): Type 'never[]' has no properties in common with type 'EmptyObject'.

IsEmptyObject

Signature

export type IsEmptyObject<T, True = true, False = false> = [T] extends [never]
  ? False
  : boolean extends (T extends never ? true : false) ? False
  : [T] extends [EmptyObject] ? True
  : T extends object ? object extends T ? False
    : [Exclude<keyof T, kEmptyObject>] extends [never] ? True
    : False
  : False;

Type-level predicate that checks if a value is an empty object. This is the type equivalent of the isEmptyObject function.

It also supports custom true/false types, allowing you to construct your own type guards with the desired return type, or create conditional types that depend on the emptiness of an object.

Type Parameters
  • T
  • True (default: true)
  • False (default: false)
Categories

Objects Type Guards

See Also

Examples

import type { IsEmptyObject } from "jsr:@nick/is/empty-object";

type A = IsEmptyObject<{}>; // true
type B = IsEmptyObject<{ a: 1 }>; // false
type C = IsEmptyObject<[]>; // false
import type { IsEmptyObject } from "jsr:@nick/is/empty-object";

type PickEmptyObjectProperties<T> = {
  [K in keyof T as IsEmptyObject<T[K], K, never>]: T[K];
  // shorthand conditionals       true ^  ^ false
  // equivalent to: IsEmptyObject<T[K]> extends true ? K : never
};
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