In JavaScript, the prototype object is a mechanism that allows you to add properties and methods to all instances of a particular object type. Every JavaScript object has a prototype property, which references the prototype object associated with it.

Here’s an example of using the prototype object to add properties and methods to objects:

// Constructor function for creating Person objects
function Person(name, age) {
  this.name = name;
  this.age = age;
}

// Adding a method to the prototype object of Person
Person.prototype.greet = function() {
  console.log('Hello, my name is ' + this.name + ' and I am ' + this.age + ' years old.');
};

// Creating instances of Person
var person1 = new Person('John', 25);
var person2 = new Person('Jane', 30);

// Calling the greet method on the instances
person1.greet(); // Output: Hello, my name is John and I am 25 years old.
person2.greet(); // Output: Hello, my name is Jane and I am 30 years old.

In the example above, the Person function acts as a constructor for creating Person objects. We add properties name and age to each instance using the this keyword inside the constructor.

Next, we use the prototype property of the Person function to add a greet method to the prototype object. This means that all instances of Person objects will have access to the greet method through their prototype chain.

Note that the concept of prototypes is fundamental to JavaScript’s object-oriented programming model based on prototypal inheritance. It enables objects to inherit properties and methods from their prototypes, creating a chain of objects with shared functionality.