isObject

Determine if a value is an Object

Usage

Pass in a value and get a boolean telling you if the value is a plain object, a custom class instance, or an object with a null prototype.

This function returns false for arrays, functions, and built-in object types like Date, RegExp, Map, and Set.

import * as 
import _
_ from 'radashi'

class 
class Data
Data {}

import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject({}) // => true
import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject(
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.create(o: object | null): any (+1 overload)
Creates an object that has the specified prototype or that has null prototype.
@param ― o Object to use as a prototype. May be null.
create(null)) // => true
import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject(new 
constructor Data(): Data
Data()) // => true

import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject([]) // => false
import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject(new 
var Date: DateConstructor
new () => Date (+3 overloads)
Date()) // => false
import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject(() => {}) // => false
import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject(null) // => false

TypeScript narrowing

This is a good fit for accepting either an options object or a primitive shorthand.

import * as 
import _
_ from 'radashi'

type 
type Options = {
    foo?: string;
}
Options = { 
foo?: string
foo?: string }

declare let 
let value: string | Options | undefined
value: 
type Options = {
    foo?: string;
}
Options | string | undefined

const 
const options: Options
options: 
type Options = {
    foo?: string;
}
Options = 
import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject(
let value: string | Options | undefined
value)
  ? 
let value: Options
value
  : 
let value: string | undefined
value === 
var undefined
undefined
    ? {}
    : { 
foo?: string
foo: 
let value: string
value }

If a union can contain arrays, functions, or special objects, narrow those cases directly instead of starting with _.isObject.

import * as 
import _
_ from 'radashi'

type 
type Options = {
    foo?: string;
}
Options = { 
foo?: string
foo?: string }

declare const 
const value: Options | (() => Options) | Options[]
value: 
type Options = {
    foo?: string;
}
Options | (() => 
type Options = {
    foo?: string;
}
Options) | 
type Options = {
    foo?: string;
}
Options[]

if (
import _
_.
function isObject(value: unknown): value is object
Returns true if value is a plain object, a class instance
(excluding built-in classes like Date/RegExp), or an
Object.create(null) result. Objects from other realms are
also supported.
Use this as a TypeScript type guard only when the input is known to
be either an object accepted by isObject or a non-object value. The
object type in TypeScript also includes arrays, functions, dates,
maps, sets, and other object-like values that isObject may reject
at runtime.
@see ― https://radashi.js.org/reference/typed/isObject
@example 
isObject({}) // true
isObject(new Object()) // true
isObject(Object.create(null)) // true
isObject(new class {}) // true

isObject([]) // false
isObject(/.+/g) // false
isObject(new Date()) // false
isObject(new Map()) // false
isObject(new Set()) // false
@version ― 12.1.0
isObject(
const value: Options | (() => Options) | Options[]
value)) {
  value
const value: Options | (() => Options) | Options[]
} else {
  value
const value: never
}

if (
import _
_.
const isArray: <Options | (() => Options) | Options[]>(value: Options | (() => Options) | Options[]) => value is Options[]
Literally just Array.isArray but with better type inference.
@see ― https://radashi.js.org/reference/typed/isArray
@example 
isArray([]) // => true
isArray('hello') // => false
@version ― 12.1.0
isArray(
const value: Options | (() => Options) | Options[]
value)) {
  value
const value: Options[]
} else if (
import _
_.
function isFunction(value: any): value is Function
Return true if the given value is a function.
@see ― https://radashi.js.org/reference/typed/isFunction
@example 
isFunction(0) // => false
isFunction(() => {}) // => true
isFunction(function() {}) // => true
isFunction(async function() {}) // => true
isFunction(class {}) // => false
@version ― 12.1.0
isFunction(
const value: Options | (() => Options)
value)) {
  value
const value: () => Options
} else {
  value
const value: Options
}