Explain Prototype Inheritance in JavaScript

Prototype Inheritance is a mechanism in JavaScript that allows objects to inherit properties and methods from other objects. In JavaScript, every object has a prototype object, which acts as a template for the object. When a property or method is accessed on an object, JavaScript first looks for it on the object itself. If it is not found, it looks for it on the object's prototype. If it is still not found, it looks for it on the prototype's prototype, and so on, until it reaches the end of the prototype chain.

There are two main ways to create objects in JavaScript: using object literals and using constructor functions.

• Object Literals: When an object is created using an object literal, its prototype is automatically set to the Object.prototype object. For example:

let person = {
  name: "John",
  age: 30,
  greet: function() {
    console.log("Hello, my name is " + this.name);
  }
};

console.log(person.name); // "John"
person.greet(); // "Hello, my name is John"
console.log(person.toString()); // "[object Object]"

In the above example, the person object is created using an object literal. Its prototype is automatically set to the Object.prototype object. The name and age properties are defined on the person object itself, while the greet method is defined on the Object.prototype object and is inherited by the person object.

• Constructor Functions: When an object is created using a constructor function, its prototype is set to the constructor function's prototype property. For example:

function Person(name, age) {
  this.name = name;
  this.age = age;
}

Person.prototype.greet = function() {
  console.log("Hello, my name is " + this.name);
};

let person = new Person("John", 30);

console.log(person.name); // "John"
person.greet(); // "Hello, my name is John"
console.log(person.toString()); // "[object Object]"

In the above example, the Person constructor function is defined with a name and age parameter. The greet method is defined on the Person.prototype object. When a new Person object is created using the new keyword, its prototype is set to the Person.prototype object. The name and age properties are defined on the person object itself, while the greet method is inherited from the Person.prototype object.

In summary, prototype inheritance allows objects to inherit properties and methods from other objects. It is a powerful feature of JavaScript that allows for code reuse and object-oriented programming.