Class Properties and Initialization
123456789101112131415class 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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Can you explain what happens if I don't initialize a property in the constructor or with a default value?
How can I add more properties to the Person class?
What is the difference between public, private, and protected properties in TypeScript classes?
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123456789101112131415class 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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