How to check variable is an object in JavaScript?

In the JavaScript world, any value is either an object or a primitive value. We know that JavaScript has 7 primitive data types: string, number, bigint, boolean, undefined, symbol, and null. Primitive data is not an object and has no methods.

What is an object?

In JavaScript, an object is a standalone entity, with properties and type. Following are some of the examples of objects:

• {“a”: 1, “b”: 2} — objects created using literal notation
• Object.prototype
• everything descended from Object.prototype
• Function.prototype
• Object
• Function
• function getUser(){} — user-defined functions
• getUser.prototype — the prototype property of a user-defined function
• new getUser() — “new”-ing a user-defined function
• Math
• Array.prototype

a

• arrays
• new Number(3) — wrappers around primitives
• Object.create(null)
• everything descended from an Object.create(null)
• … others

is object

As we know the array, function, etc are objects. The following code will check a variable is an object including array, function, etc. It only excludes null.

typeof variable === 'object' && variable !== null

If we want to exclude arrays we need to add a check for arrays too. Following is the code that excludes arrays.

typeof variable === 'object' && variable !== null && !Array.isArray(variable)