What are classes in javascript?

Q: What are classes in javascript?

**Kind:** Getter, setter, method, or field **Location:** Static or instance **Visibility:** Public or private // Class Declaration class SpaceStation { constructor(name, orbit) { this.name = name; this.orbit = orbit; } getDetails() { return `${this.name} is orbiting ${this.orbit}.`; } } const iss = new SpaceStation("ISS", "Earth"); console.log(iss.getDetails()); // "ISS is orbiting Earth." // Unnamed Class Expression const Rectangle = class { constructor(height, width) { this.height = height; this.width = width; } area() { return this.height * this.width; } }; // Named Class Expression const Polygon = class NamedPolygon { getName() { return NamedPolygon.name; // "NamedPolygon" is accessible here } };

Difficulty: 5/10

class syntax, inheritance, static members

Classes are a template for creating objects. They encapsulate data with code to work on that data. Classes are in fact 'special functions', and just as you can define function expressions and function declarations, a class can be defined in two ways: a class expression or a class declaration. The body of a class is executed in strict mode even without the 'use strict' directive.

A class element can be characterized by three aspects:

1
Kind: Getter, setter, method, or field
2
Location: Static or instance
3
Visibility: Public or private

javascript

Scenario Questions

0-2 years experience

1We need to add a simple User model with a name and email. How would you define a class for it in JavaScript, and how would you create an instance?
2If you call a method defined on a class without using 'new', what happens? Show with a short example.

2-5 years experience

1Our feature uses a base class 'Shape' and derived classes 'Circle' and 'Rectangle'. We noticed that overriding a method in Rectangle doesn't get called. What could be causing this, and how would you fix it?

Follow-up Questions

Can you walk me through what happens under the hood when you instantiate a class?
How would you expose private data in a class before private fields were standardized?
What are the differences between using a class and a factory function for creating objects?