Summary  
This chapter explains how to declare class properties with or without default values in TypeScript and how to initialize unassigned properties using the constructor so that each instance gets its own values.

General domain of usage  
Object-oriented modeling of entities in applications.

class Person {
  name: string = "John"; // Property with a default value
  age: number;           // Property without a default value
  isEmployed: boolean;   // Property without a default value

  constructor(age: number, isEmployed: boolean) {
    this.age = age;             // Initialize property in constructor
    this.isEmployed = isEmployed;
  }
}

const person1 = new Person(30, true);
console.log(person1.name);        // Output: John
console.log(person1.age);         // Output: 30
console.log(person1.isEmployed);  // Output: true

When working with **TypeScript classes**, you can declare properties directly inside the class body. Properties can be given **default values**, or you can leave them uninitialized and assign values later, usually in the `constructor`. Declaring a property with a default value means every instance of the class starts with that value unless it is overwritten. If you do not provide a default value, you must assign one—typically in the `constructor`—so that each instance can have its own value.

Using the `constructor` to initialize properties is especially useful for properties that should be set differently for each instance. This ensures that every object created from the class has its own unique set of property values, rather than sharing a single value across all instances.

What is the main advantage of initializing class properties in the constructor?

Learn how TypeScript leverages object-oriented programming concepts to create structured, reusable, and type-safe code. Explore classes, properties, methods, access modifiers, encapsulation, inheritance, polymorphism, interfaces, and generics with practical examples.

Class Properties and Initialization