Impara Class Properties and Initialization


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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.

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Sezione 1. Capitolo 2

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              123456789101112131415
            
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

Tutto è chiaro?

Grazie per i tuoi commenti!

Sezione 1. Capitolo 2