Check if a value is an object in JavaScript

If typeof yourVariable === 'object', it's an object or null.

If you want null, arrays or functions to be excluded, just make it:

if (    typeof yourVariable === 'object' &&    !Array.isArray(yourVariable) &&    yourVariable !== null) {    executeSomeCode();}

UPDATE:

This answer is incomplete and gives misleading results. For example, null is also considered of type object in JavaScript, not to mention several other edge cases. Follow the recommendation below and move on to other "most upvoted (and correct!) answer":

typeof yourVariable === 'object' && yourVariable !== null

Original answer:

Try using typeof(var) and/or var instanceof something.

EDIT: This answer gives an idea of how to examine variable's properties, but it is not a bulletproof recipe (after all there's no recipe at all!) for checking whether it's an object, far from it. Since people tend to look for something to copy from here without doing any research, I'd highly recommend that they turn to the other, most upvoted (and correct!) answer.

Let's define "object" in Javascript. According to the MDN docs, every value is either an object or a primitive:

primitive, primitive value

A data that is not an object and does not have any methods. JavaScript has 7 primitive data types: string, number, bigint, boolean, undefined, symbol, and null.

What's a primitive?

• 3
• 'abc'
• true
• null
• undefined

What's an object (i.e. not a primitive)?

• Object.prototype
• everything descended from Object.prototype
  • Function.prototype
    • Object
    • Function
    • function C(){} -- user-defined functions
  • C.prototype -- the prototype property of a user-defined function: this is not Cs prototype
    • new C() -- "new"-ing a user-defined function
  • Math
  • Array.prototype
    • arrays
  • {"a": 1, "b": 2} -- objects created using literal notation
  • new Number(3) -- wrappers around primitives
  • ... many other things ...
• Object.create(null)
• everything descended from an Object.create(null)

How to check whether a value is an object

instanceof by itself won't work, because it misses two cases:

// oops:  isObject(Object.prototype) -> false// oops:  isObject(Object.create(null)) -> falsefunction isObject(val) {    return val instanceof Object; }

typeof x === 'object' won't work, because of false positives (null) and false negatives (functions):

// oops: isObject(Object) -> falsefunction isObject(val) {    return (typeof val === 'object');}

Object.prototype.toString.call won't work, because of false positives for all of the primitives:

> Object.prototype.toString.call(3)"[object Number]"> Object.prototype.toString.call(new Number(3))"[object Number]"

So I use:

function isObject(val) {    if (val === null) { return false;}    return ( (typeof val === 'function') || (typeof val === 'object') );}

@Daan's answer also seems to work:

function isObject(obj) {  return obj === Object(obj);}

because, according to the MDN docs:

The Object constructor creates an object wrapper for the given value. If the value is null or undefined, it will create and return an empty object, otherwise, it will return an object of a type that corresponds to the given value. If the value is an object already, it will return the value.

A third way that seems to work (not sure if it's 100%) is to use Object.getPrototypeOf which throws an exception if its argument isn't an object:

// these 5 examples throw exceptionsObject.getPrototypeOf(null)Object.getPrototypeOf(undefined)Object.getPrototypeOf(3)Object.getPrototypeOf('abc')Object.getPrototypeOf(true)// these 5 examples don't throw exceptionsObject.getPrototypeOf(Object)Object.getPrototypeOf(Object.prototype)Object.getPrototypeOf(Object.create(null))Object.getPrototypeOf([])Object.getPrototypeOf({})