In JavaScript, the constructor method is a special method that is automatically called when a new instance of a class or an object is created. It’s used to initialize the newly created object with default values or to perform any necessary setup tasks.
Usage in ES6 Classes:
- In ES6, the
constructormethod is used within class definitions to define the initialization logic for objects created with the class. - It’s a reserved keyword and must be spelled exactly as
constructor. - The
constructormethod is optional. If not provided, a default constructor is used implicitly.
class ClassName {
constructor(/* constructor parameters */) {
// Constructor logic
}
}
Parameters:
- The
constructormethod can accept parameters, which are passed when creating new instances of the class. These parameters are used to customize the initialization of each instance.
class Person {
constructor(name, age) {
this.name = name;
this.age = age;
}
greet() {
console.log(`Hello, my name is
${this.name} and I am ${this.age} years old.`);
}
}
// Creating instances of the Person class
let person1 = new Person("Alice", 30);
let person2 = new Person("Bob", 25);
person1.greet();
// Output: Hello,
my name is Alice and I am 30 years old.
person2.greet();
// Output: Hello, my name is Bob and
I am 25 years old.
Initialization Logic:
- Inside the
constructormethod, you can perform any necessary setup tasks such as initializing instance properties, setting default values, or calling other methods.
Automatically Called:
- The
constructormethod is automatically called when you use thenewkeyword to create a new instance of a class or an object.
Return Value:
- The
constructormethod does not return anything explicitly. Its main purpose is to initialize the newly created object.
Use Cases:
- Initializing instance properties with default values.
- Performing setup tasks that need to be done whenever a new object is created.
