The Object preventExtensions() method

Find out all about the JavaScript preventExtensions() method of the Object object

⭐️ 👀 2023 WEB DEVELOPMENT BOOTCAMP starting in days! Join the waiting list to reserve your spot in my 10-weeks cohort course and learn the fundamentals, HTML, CSS, JS, Tailwind, React, Next.js and much much more! 👀 ⭐️

The JavaScript preventExtensions() method of the Object object takes an object as argument, and returns the same object. The object passed as argument is mutated and it’s now an object that will not accept new properties. New properties can’t be added, but existing properties can be removed, and existing properties can be changed.


const dog = {}
dog.breed = 'Siberian Husky'
Object.preventExtensions(dog) = 'Roger' //TypeError: Cannot add property name, object is not extensible

The argument passed as argument is also returned as argument, hence dog === myDog (it’s the same exact object).

We can’t add new properties, but we can remove existing properties:

const dog = {}
dog.breed = 'Siberian Husky' = 'Roger'
dog //{ breed: 'Siberian Husky' }

One more thing! ⚠️ ✋

At the end of January I will organize the Web Development Bootcamp.

It's a 10-weeks long cohort online course where I will guide you to becoming a Web Developer.

It's not "just a course". It's a big event I organize once a year.

We'll start from zero, learn the fundamentals of Web Development, HTML CSS, JavaScript, Tailwind, Git, using the command line, VS Code, GitHub, Node.js, we'll then learn React, JSX, how to use PostgreSQL, Astro, Next.js, Prisma, deploying on Netlify/DigitalOcean/Fly/Vercel and much more! 

At the end of the first 10 weeks you'll know how to create web sites and web applications and I'll unlock you the 2nd phase of the Bootcamp: you will get access to a large number of projects exclusive to the Bootcamp graduates, so you can follow my instructions to build things like private areas with authentication, clones of popular sites like Twitter YouTube Reddit, create e-commerce sites, and much much more.

Because once you got the fundamentals, you only learn by working on real, exciting projects.

To find out more, visit