Important JavaScript Object Methods Every Developer Should Know

Important JavaScript Object Methods Every Developer Should Know
August 21, 2023

JavaScript is like the magic wand of the web, bringing websites to life with dynamic interactions. At the heart of this enchantment lies the humble object. Objects are like tiny treasure chests, holding various pieces of data. But they're more than passive containers.

Thanks to object methods, they can perform tasks, make decisions, and interact with other elements.

Let's dive into some of these essential methods, shall we?

1. keys()

This method retrieves the names of all the enumerable properties from an object.

It's handy when you need to iterate over properties or when you just want to get a quick overview of the object's structure.

const car = { make: 'Toyota', model: 'Camry' };
console.log(Object.keys(car)); // ['make', 'model']

2. values()

This method, similar to Object.keys(), gives you the values instead of the keys.

It's particularly useful when you are more interested in the data stored rather than their property names.

console.log(Object.values(car)); // ['Toyota', 'Camry']


This method combines both keys and values to produce an array of pairs. Each pair, represented by an array, consists of a property name followed by its corresponding value.

This can be beneficial when working with functions that expect  key-value pairs.

console.log(Object.entries(car)); // [['make', 'Toyota'], ['model', 'Camry']]

4. assign()

It's like a photocopier for objects. This method is used to copy values from one or more source objects to a target object.

It's essential when you need to merge objects or create copies with additional properties.

const details = { color: 'red' };
const carWithDetails = Object.assign(car, details);
console.log(carWithDetails); // { make: 'Toyota', model: 'Camry', color: 'red' }

5. freeze()

Think of this as a protective shield for your object.

Once an object is frozen, you can't add, delete, or modify its properties. It's useful when you want to ensure data integrity.

car.year = 2020; // Throws an error because car is frozen.


This method is a bit more lenient than Object.freeze(). While you still can't add or delete properties, you can modify the values of existing properties.

It's a midway solution when you want some flexibility without adding new properties.

car.make = 'Honda'// Works fine
car.year = 2020;     // Throws an error since you can't add new properties.

7. hasOwnProperty()

This method checks if an object has a specific property as its direct property (not inherited from its prototype).

It's a safer way to check for properties than using the in-operator, especially when working with objects that might have overridden built-in properties.

console.log(car.hasOwnProperty('make')); // true

8. is()

While it may look like the strict equality (===) operator, this method has some nuanced differences, especially when comparing NaN values.

It checks if two values are the same, including distinguishing between positive and negative zeros.

console.log('hello', 'hello')); // true
console.log(, NaN)); // true (whereas NaN === NaN returns false)

9. defineProperty()

This method is your advanced tool for adding new properties or modifying existing ones.

You can set characteristics like enumerability, writability, and configurability for the property, offering fine-grained control over its behavior.

Object.defineProperty(car, 'year', { value: 2020, writable: false });
console.log(car.year); // 2020

10. create()

This method lets you create a fresh object while specifying its prototype.

It's a powerful way to implement inheritance in JavaScript, allowing you to create new objects that inherit properties and methods from existing objects.

const newCar = Object.create(car);
console.log(newCar.make); // 'Toyota'

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