How to Get the Length of Object in JavaScript

Kirill Ibrahim Feb 02, 2024 JavaScript JavaScript Object
  1. Use the Object.keys() Method to Get the Length of an Object in JavaScript
  2. Use for... Loop to Get the Length of an Object in JavaScript
How to Get the Length of Object in JavaScript

We want to get the length of an object in JavaScript, but the Object doesn’t have a length property. Only arrays and strings have the length property.

let object1 = {name: 'Mark', age: 30};
let string1 = 'Delftstack';
let array1 = [1, 2, 3];
console.log(object1.length);
console.log(string1.length);
console.log(array1.length);

Output:

undefined
10 
3

We will introduce different methods to get the length of an object in JavaScript.

Use the Object.keys() Method to Get the Length of an Object in JavaScript

The Object.keys() method returns an array of properties of the Object. We use the length property to get the number of keys.

Example:

const getLengthOfObject =
    (obj) => {
      let lengthOfObject = Object.keys(obj).length;
      console.log(lengthOfObject);
    }

getLengthOfObject({id: 1, name: 'Mark', age: 30});

Output:

3

Use for... Loop to Get the Length of an Object in JavaScript

It iterates the properties of the object and will increase the counter of properties in the loop.

Example:

const getLengthOfObject =
    (obj) => {
      let length0fObject = 0;

      for (let key in obj) {
        length0fObject++;
      }

      console.log(length0fObject);
      return length0fObject;
    }

getLengthOfObject({id: 1, name: 'Mark', age: 30});

Output:

3

Example:

const getLengthOfObject =
    (obj) => {
      let length0fObject = 0;

      for (let key in obj) {
        if (obj.hasOwnProperty(key)) {
          length0fObject++;
        }
      }

      console.log(length0fObject);
      return length0fObject;
    }

getLengthOfObject(
    {id: 1, name: 'Mark', age: 30, country: 'USA', job: 'software developer'});

The hasOwnProperty() function is a built-in function in JavaScript is used to check if the object owns the specified property. it returns a true or false depending on if the object has the specified property or not.

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