JavaScript Object Constructor

• An object constructor is a function that is used to create and initialize objects.
• It defines a template for objects with properties and methods.

Syntax:

function ObjectName(property1, property2, /* ... */) {
  this.property1 = property1;
  this.property2 = property2;
  // ...
  this.methodName = function(/* ... */) {
    // Code to be executed
  };
}

• ObjectName: The name of the object constructor function.
• property1, property2, ...: Parameters used to initialize properties.
• methodName: A method (function) associated with the object.

Why it is Used:

• Object Initialization: Provides a way to create objects with predefined properties and methods.
• Code Reusability: Enables the reuse of the object structure by creating multiple instances.

Example:

// Object Constructor Function for Cars
function Car(make, model, year) {
  this.make = make;
  this.model = model;
  this.year = year;

  this.displayInfo = function() {
    console.log(`Make: ${this.make}, Model: ${this.model}, Year: ${this.year}`);
  };
}

// Creating Instances of the Car Object
const car1 = new Car('Toyota', 'Camry', 2022);
const car2 = new Car('Honda', 'Accord', 2021);

// Calling Object Methods
car1.displayInfo(); // Output: Make: Toyota, Model: Camry, Year: 2022
car2.displayInfo(); // Output: Make: Honda, Model: Accord, Year: 2021

Object Constructor with Prototypes: To improve memory efficiency, you can define methods on the object's prototype.

function Car(make, model, year) {
  this.make = make;
  this.model = model;
  this.year = year;
}

// Adding a Method to the Object's Prototype
Car.prototype.displayInfo = function() {
  console.log(`Make: ${this.make}, Model: ${this.model}, Year: ${this.year}`);
};

Object Constructor for Creating Instances:

// Object Constructor for Creating Instances
function createPerson(firstName, lastName, age) {
  return {
    firstName: firstName,
    lastName: lastName,
    age: age,
    greet: function() {
      console.log(`Hello, ${this.firstName} ${this.lastName}!`);
    }
  };
}

// Creating Instances using the Object Constructor
const person1 = createPerson('John', 'Doe', 30);
const person2 = createPerson('Alice', 'Smith', 25);

// Calling Object Methods
person1.greet(); // Output: Hello, John Doe!
person2.greet(); // Output: Hello, Alice Smith!

 

Summary

• Object constructors are functions used to create and initialize objects.
• They define a template for objects with properties and methods.
• Object constructors are invoked using the new keyword to create instances.
• Methods can be defined directly within the constructor or on the object's prototype for memory efficiency.
• Object constructors are a key concept in object-oriented programming and enable the creation of multiple instances with shared structures.