Object/Since 1.38.0

has

Checks whether an object has its own property with the specified key.

has(object, key):boolean

Own properties

The function checks only whether the key belongs directly to the object. Properties inherited through the prototype chain are not considered.

PropertyKey

The key parameter uses the PropertyKey type, so string, number, and symbol keys can be checked.

Undefined properties

A property whose value is undefined still counts as an existing property. The function checks whether the key exists, not whether its value is defined.

Parameters

objectTrequired

The object to check.

keyPropertyKeyrequired

The property key to check. It can be a string, number, or symbol.

Returns

boolean

true if the object has the specified key as its own property; otherwise, false.

Examples

Basic usage

TypeScript

const user = {
  name: "Amir",
  age: 22,
};

has(user, "name");
// true

has(user, "email");
// false

Own properties only

TypeScript

const parent = {
  name: "Amir",
};

const user = Object.create(parent);

has(user, "name");
// false

Inherited properties

TypeScript

const parent = {
  role: "admin",
};

const user = Object.create(parent);

has(user, "role");
// false

Undefined values

TypeScript

const data = {
  value: undefined,
};

has(data, "value");
// true

Null values

TypeScript

const data = {
  value: null,
};

has(data, "value");
// true

Symbol keys

TypeScript

const id = Symbol("id");

const user = {
  [id]: 123,
};

has(user, id);
// true

Numeric keys

TypeScript

const data = {
  1: "one",
};

has(data, 1);
// true

Falsy values

TypeScript

const data = {
  count: 0,
  active: false,
  name: "",
};

has(data, "count");
// true

has(data, "active");
// true

has(data, "name");
// true

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