JavaScript Prototype

Syntax

objectName.prototype.propertyName = value;

Example

function Person(firstName, lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
}

Person.prototype.fullName = function() {
  return this.firstName + " " + this.lastName;
};

var person1 = new Person("John", "Doe");
console.log(person1.fullName()); // Output: John Doe

Output

John Doe

Explanation

In JavaScript, every object has a prototype property that allows us to add properties and methods to that object. Prototype is a way to create objects that share properties and methods. It is like a blueprint for creating objects.

In the above example, we have created a Person constructor function that takes firstName and lastName as parameters. We have added a fullName method to the Person prototype which returns the full name of the person.

We have then instantiated a person1 object and called the fullName method on it to get the full name of the person.

Use

JavaScript prototype is used to add properties and methods to an object such that all objects that are created using the constructor function share the properties and methods defined in the prototype.

Important Points

• Every object has a prototype property that allows us to add properties and methods to that object.
• Prototype is a way to create objects that share properties and methods.
• Prototypes are used to add properties and methods to objects created using constructor functions.
• Always define methods on the prototype object to save memory space and improve performance.

Summary

In JavaScript, prototype is a way to add properties and methods to objects. It is a blueprint for creating objects that share properties and methods. We can add properties and methods to objects by setting them on the prototype property of the object's constructor function. Using prototypes helps to save memory space and improve performance.