Classes in TypeScript

classes-in-typescript.md

Classes in TypeScript

Types of properties

• public(the default case)

• private

  • you can only access it from the class. Cannot set/read it from outside.

  class Human {
    private type: string = "terran";
    constructor(public name: string) {
      this.name = name;
    }
  }
  const ivan = new Human("Ivan");
  
  // Error: Property 'type' is private and only accessible within class 'Human'
  console.log(ivan.type);
  

  class Human {
    private type: string = "terran";
    constructor(public name: string) {
      this.name = name;
    }
    public getType(): string {
      console.log(this.type);
      return this.type;
    }
  }
  const ivan = new Human("Ivan");
  
  // no error: the return value will be terran
  ivan.getType();
  
  

• protected

  • behaves like private type and all objects that inherit can access those kind of properties

Getters and Setters

Example of using a getter

class User {
  private _membership = "standard";

  constructor(public name: string) {
    this.name = name;
  }

  set membership(value: string) {
    this._membership = value;
  }

  get membership(): string {
    return this._membership;
  }
}

const ivan = new User("Ivan");

const ivanMembership = ivan.membership;
console.log(ivanMembership); // standard

Example of using a setter

class User {
  private _membership = "standard";

  constructor(public name: string) {
    this.name = name;
  }

  set membership(value: string) {
    this._membership = value;
  }

  get membership(): string {
    return this._membership;
  }
}

// create the new user
const ivan = new User("Ivan");

// set user's membership
ivan.membership = "premium";

// get user's membership
const ivanMembership = ivan.membership;
console.log(ivanMembership);

The same setter example from above compiled to vanilla ES6

"use strict";
class User {
    constructor(name) {
        this.name = name;
        this._membership = "standard";
        this.name = name;
    }
    set membership(value) {
        this._membership = value;
    }
    get membership() {
        return this._membership;
    }
}
// create the new user
const ivan = new User("Ivan");
// set user's membership
ivan.membership = "premium";
// get user's membership
const ivanMembership = ivan.membership;
console.log(ivanMembership);

Static properties and methods

class Dashboard {
  static version = "1.0.0";
  static getVersion() {
    return this.version;
  }
}

console.log(`Version: ${Dashboard.version}`);

const currentVersion = Dashboard.getVersion();
console.log(currentVersion);

// the result from both logs will be: 1.0.0

Static properties and methods(compiled to vanilla ES6)

"use strict";
class Dashboard {
    static getVersion() {
        return this.version;
    }
}
Dashboard.version = "1.0.0";
console.log(`Version: ${Dashboard.version}`);
const currentVersion = Dashboard.getVersion();
console.log(currentVersion);