Popular:
 Building Resilient Systems on AWS: Learn how to design and implement a resilient, highly available, fault-tolerant infrastructure on AWS.

Object.freeze: Immutable Objects

By  on  

One of my favorite part of JavaScript has always been mutability of objects.  I loved that MooTools and likewise frameworks could modify native prototypes to enhance them with functionality we knew the language need; in fact, I credit MooTools with pushing the web forward.

There are cases, however, where you don't want an object to be modifiable; you don't want values for existing properties to be changed, added, or removed.  That's where Object.freeze can help -- with Object.freeze you can create immutable objects you can trust!

const obj = Object.freeze({
    x: 1,
    y: 2
});

// None of these do anything
obj.x = 8; // { x: 1, y: 2}
delete obj.x; // { x: 1, y: 2}
obj.z = 3;  // { x: 1, y: 2}

Object.freeze is a welcomed addition to JavaScript and a necessary one.  If you have objects whose integrity you want to secure, immutability is required.  Object.seal provides similar functionality without the ability to freeze values, so Object.freeze is your best choice when you want to lock down an object!

Request Metrics real user monitoring
Request Metrics real user monitoring
Request Metrics real user monitoring
Request Metrics real user monitoring

Recent Features

  • By
    CSS @supports

    Feature detection via JavaScript is a client side best practice and for all the right reasons, but unfortunately that same functionality hasn't been available within CSS.  What we end up doing is repeating the same properties multiple times with each browser prefix.  Yuck.  Another thing we...

  • By
    Send Text Messages with PHP

    Kids these days, I tell ya.  All they care about is the technology.  The video games.  The bottled water.  Oh, and the texting, always the texting.  Back in my day, all we had was...OK, I had all of these things too.  But I still don't get...

Incredible Demos

  • By
    Cross Browser CSS Box Shadows

    Box shadows have been used on the web for quite a while, but they weren't created with CSS -- we needed to utilize some Photoshop game to create them.  For someone with no design talent, a.k.a me, the need to use Photoshop sucked.  Just because we...

  • By
    Animated AJAX Record Deletion Using MooTools

    I'm a huge fan of WordPress' method of individual article deletion. You click the delete link, the menu item animates red, and the item disappears. Here's how to achieve that functionality with MooTools JavaScript. The PHP - Content & Header The following snippet goes at the...

Discussion

  1. Shallow

    It’s good to remind that Object.freeze does only shallow freeze.

  2. Varghese

    That’s a nice feature. Much needed. However, I hope the browser support is good.

  3. MaxArt

    Should I remind that MooTools’ practice to extend native prototypes prevented W3C to use well-known names like contains and flatten, because it would have literally broken the web?
    Extending native prototypes is the last thing you’d want in a general purpose library.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!