How to Get the Length of an Object in JavaScript?

Introduction

Objects are collections of key-value pairs that have properties that are linked by their names. Understanding how to find the object's length is not a common and basic operation, but in order to avoid unnecessary bugs, it is essential to know how it can be done. There is no length property by default on the object. It is only available to arrays and strings that have the length property. A JavaScript object's length can be determined by either using one of its static methods or by using the for...in loop method. Let us explore them one by one

Method 1: Using the Object.keys() Method

An object's length can be obtained by calling the Object.keys() method and accessing the length property, such as Object.keys(obj).length. A given object's key name is returned by Object.keys(); its length is returned by its length property.

Syntax:

Example:

This example shows how we can find the length of an object with three fields using Object.keys().

Output:

Method 2: How to Loop through All the Fields of the Object and Check Their Property

A boolean value is returned by the hasOwnProperty() method indicating whether the specified property belongs to the object. It is possible to check whether each key is present within the object by using this method. Each key in the object is looped through, and if it is present, the total number of keys is increased. In this way, you can find out the object's length from this.

Example:

This example shows how we can loop through the object with three fields using the hasOwnProperty() method. We loop through all the 3 fields inside the user and display it as output using hasOwnProperty() method.

Output:

Get Length of Object with Object.values()

The Object.values() method returns a list of the enumerable property values associated with the object. As a next step, we will use the object's length property to determine how many elements there are in the array (length of the object).

Syntax:

Example:

This example shows how we can find the length of an object with three fields using Object.values().

Output:

Get Length of Object with Object.entries()

The Object.entries() method returns a collection of string-keyed properties [key, value] on your object. We will then use the length property to determine the number of elements.

Syntax:

Example:

This example shows how we can find the length of an object with three fields using Object.entries().

Output:

Get Length of Object Using for…in Loop

In the for...in statement, all enumerable properties of an object, including inherited enumerable properties, are iterated over (ignoring ones keyed by symbols).

Example:

This example shows how we can find the length of an object with three fields using for..in the loop.

Output:

Object.keys vs Object.getOwnPropertyNames

The Object.getOwnPropertyNames() method returns the names of all the properties owned by an object. The Object.keys() method returns all the object's enumerable properties. If you don't set enumerable: false to any property, both return the same result.

The student object has two properties, including its name and age.

Let's define another property named Class but set it to enumerable: false:

In JavaScript, a property is enumerable if it can be read while being iterated using the for...in the loop or the Object. keys() function.

Object.keys do not include the resolution property:

Object Length with Symbols

The symbol primitive data type was introduced in ECMAScript 6. It returns an array of all symbol properties found directly on an object using the getOwnPropertySymbol() method.

Example:

Example:

This example shows how we can find the length of an object with three fields using getOwnPropertySymbol() method.

Output:

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