DEV Community

Cover image for JS interview in 2 minutes / Encapsulation (OOP)
Nick K
Nick K

Posted on • Updated on

JS interview in 2 minutes / Encapsulation (OOP)

What is Encapsulation?

Quick answer:
Encapsulation can be used in any meaning of any of these terms or both:

  • Mechanism used to restrict access to some of an object's properties.
  • Mechanism that allows data access only via related methods or functions (setters and getters).

Longer answer:
Basically, the first definition is only about creating private properties.

Btw there are no private properties in JavaScript but looks like there is a proposal. In Typescript private properties are present.

UPD: as @scott_yeatts has mentioned in the comments, it is still possible to use private properties in JavaScript via The Revealing Module Pattern.


Another definition is just a way to say that access to every property is implemented via getters and setters.

class User {
  private salary = 0;

  setSalary(salary: number) {
    this.salary = salary

  getSalary() {
    return this.salary

let user = new User()
console.log(user.getSalary()) // 0
console.log(user.getSalary()) // 10
Enter fullscreen mode Exit fullscreen mode

Real-life applications:
This getters & setters pattern was always confusing to me and felt like a total redundancy, haven't changed my opinion still.

There is a list with a bunch of good reasons why getters & setters can be useful, but I can't say that I actually had an issue with any of the described topics.

// Here goes super opinionated section

Feels like the whole industry is moving to not deeply using OOP and preferring immutable objects and pure functions over data mutations, so this topic maybe just a tribute to old times 🤷

// end of super opinionated section

If you know a good example of beneficial use of getters and setters, please share it in the comments 🙏


Other posts:

Btw, I will post more fun stuff here and on Twitter. Let's be friends 👋

Top comments (2)

scott_yeatts profile image
Scott Yeatts

While it's true that JS doesn't have private properties, but this is a solved problem (No Typescript necessary!)

Use the Revealing Module design pattern, and you can have a public/private API for your module.

That said, I also believe JavaScript is trending more towards the Functional Programming world, and I'm an advocate for that direction. That doesn't mean that OOP is outdated or not something to learn, just that I don't think it's the best fit for most (but not all) JS applications.

I can't wait for the industry to reach a better balance between functional approaches, which are GREAT for stateless, event driven actions (IE: Your typical microservices web backend) and OOP which are much better suited for stateful, context dependent actions (Like you might see in an application designed to run independently without API support, like a desktop app or a game).

Both are useful, but I've seen a lot of people trying to use one or the other as a hammer, when all they have are a box of screws!

hexnickk profile image
Nick K

Thanks for the comment! I've added a note about the Revealing Module pattern to the post itself and mentioned you 🙏 Thanks again!

Both are useful, but I've seen a lot of people trying to use one or the other as a hammer when all they have are a box of screws!

Totally agree with you, the right tool, for the right need!