Extend: The JavaScript / jQuery extend method copies all properties from the source to the destination object. The primary use of the extend method is in class declarations with the purpose of creating a class (sub-class) that is the child of another parent class (super-class). It can be used to subclass both the built-in objects as well as the user-defined (custom) classes.
Syntax:
class child_class extends parent_class {
// class definition goes here
}
Example:
Javascript
// Parent Class class Animal { constructor(name) { this.name = name; } } // Child Class class Dog extends Animal { constructor(name) { // the super keyword to used to call // the constructor of the parent class super(name); this.name = name; } } |
Prototype: The prototype property is a unique feature of the JavaScript language. The prototype property acts as a member of objects. Its primary use is to allow the addition of new properties (members or functions) to object constructors. It is also used to inherit features from one to another. The need for prototyping arises because JavaScript does not allow addition of new property to an existing object constructor.
Syntax:
ClassName.prototype.property = value;
// For class members:
ClassName.prototype.member_name = member_value;
// For class methods:
ClassName.prototype.function_name = function() {
// function definition
};
Example:
Javascript
class Employee { let firstName; let lastName; // constructor Employee (first, last) { this.firstName = first; this.lastName = last; } } // add class data member Employee.prototype.email = "example@gmail.com"; // add class member function Employee.prototype.fullName = function() { return this.firstName + " " + this.lastName; }; |
