How to find Length of a JavaScript object?

Built-in Methods:

1. Object.keys().length:
js
const myObject = {name: "John", age: 30};
const length = Object.keys(myObject).length;
console.log(length); // Output: 2


2. Object.values().length:
js
const myObject = {name: "John", age: 30};
const length = Object.values(myObject).length;
console.log(length); // Output: 2


3. Object.entries().length:
js
const myObject = {name: "John", age: 30};
const length = Object.entries(myObject).length;
console.log(length); // Output: 2


Accepted Best Practice:

4. Array.from(Object.keys(myObject)).length:
js
const myObject = {name: "John", age: 30};
const length = Array.from(Object.keys(myObject)).length;
console.log(length); // Output: 2


This method creates an array from the object's keys, then gets the length of that array. It is commonly used because it works with both modern and legacy JavaScript environments.

Built-in Method:

* Object.keys(object).length: This method returns an array of the object's keys and its length property gives the number of keys, which is equal to the object's length.




const object = {
  name: "John",
  age: 30,
  city: "New York"
};

const length = Object.keys(object).length;
console.log(length); // Output: 3

Best Practice:

* Object.entries(object).length: This method returns an array of key-value pairs as tuples. Its length property gives the number of key-value pairs, which is also the object's length. This method is considered a cleaner and more modern approach.

const object = {
  name: "John",
  age: 30,
  city: "New York"
};

const length = Object.entries(object).length;
console.log(length); // Output: 3




Other Methods:

* for...in loop: You can iterate over the object's keys using a for...in loop and count the number of iterations.

const object = {
  name: "John",
  age: 30,
  city: "New York"
};

let length = 0;
for (const key in object) {
  length++;
}
console.log(length); // Output: 3




* Object.getOwnPropertyNames(object).length: This method returns an array of the object's own property names. Its length property gives the number of own property names, which may not be the same as the object's length if it has inherited properties.

const object = {
  name: "John",
  age: 30,
  city: "New York"
};
Object.defineProperty(object, "gender", { value: "male", enumerable: false });

const length = Object.getOwnPropertyNames(object).length;
console.log(length); // Output: 3 (only counts own property names)