Added Polymorphism

JavaScript_Advance/polymorphism.js

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+// Polymorphism is one of the basic principles of object-oriented programming (OOP)
+//It is the practice of designing objects to share behavior and be able to overwrite common behaviors associated with specific ones. 
+
+// First create the class Person
+class Person {
+ constructor(name) {
+ this.name = name;
+ }
+
+ getName() {
+ return this.name
+ }
+
+ getPosition() {
+ return "Unemployed"
+ }
+}
+
+// Extend the class Person with Employee
+class Employee extends Person {
+ constructor(name, position, salary) {
+ super(name); // super() calls the constructor of Person
+
+ this.position = position;
+ this.salary = salary;
+ }
+
+ getPosition() { //overwrites the method of person
+ return this.position
+ }
+
+ getSalary() {
+ return this.salary
+ }
+}
+
+let person = new Person("James");
+let employee = new Employee("Torsten", "Developer", 45000);
+
+console.log(employee.getName()); // Output: Torsten
+console.log(person.getName()); // Output: James
+
+console.log(employee.getPosition()); // Output: Developer
+console.log(person.getPosition()); // Output: Unemployed

docs/JavaScript_Advance/polymorphism.md

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+# Polymorphism
+Polymorphism is one of the basic principles of **object-oriented programming (OOP)**. It is the practice of designing objects to share behavior and be able to overwrite common behaviors associated with specific ones. Polymorphism uses inheritance to realize this.
+
+*Related: [Inheritance](JavaScript_Basics/inheritance.md), [Classes](JavaScript_Basics/classes.md)*
+
+## Parent class
+Let's create a `class` called Person first.
+```javascript
+class Person {
+ constructor(name) {
+ this.name = name;
+ }
+
+ getName() {
+ return this.name
+ }
+
+ getPosition() {
+ return "Unemployed";
+ }
+}
+```
+
+## Child class
+We like to extend this `class` for Employees. This can be done by creating a `class` and adding `extends`.
+```javascript
+class Employee extends Person {
+ constructor(name, position, salary) {
+ super(name); // super() calls the constructor of Person
+
+ this.position = position;
+ this.salary = salary;
+ }
+
+ getPosition() { //overwrites the method of person
+ return this.position
+ }
+
+ getSalary() {
+ return this.salary
+ }
+}
+```
+
+## Output
+As you can see in the output below, `getPosition()` gets overwritten in `Employee` and `getName()` can be used from `Person` in `Employee`
+```javascript
+let person = new Person("James");
+let employee = new Employee("Torsten", "Developer", 45000);
+
+console.log(employee.getName()); // Output: Torsten
+console.log(person.getName()); // Output: James
+
+console.log(employee.getPosition()); // Output: Developer
+console.log(person.getPosition()); // Output: Unemployed
+```
+
+The above example describes the polymorphism in ECMAScript. 
+An object "Person" can be described in many forms (e.g. Employee, ...).
+
+Another example from reality about polymorphism:
+
+When I mention an Asian person, it is very abstract. It can be Japanese, Vietnamese or Indian. But they all share the typical characteristics of Asians.

docs/_sidebar.md

@@ -1,27 +1,28 @@
 - JavaScript Basics
 
-- [Variables](Javascript_Basics/variables.md)
-- [String Operation](Javascript_Basics/stringOperation.md)
-- [Comparison Operators](Javascript_Basics/comparisonOperators.md)
-- [Functions](Javascript_Basics/functions.md)
-- [Arrays](Javascript_Basics/arrays.md)
-- [Objects](Javascript_Basics/objects.md)
-- [This](Javascript_Basics/this.md)
-- [Classes](Javascript_Basics/classes.md)
-- [Inheritance](Javascript_Basics/inheritance.md)
-- [Exercise 1](Javascript_Basics/exercise-1.md)
-- [Exercise 1 Using Object](Javascript_Basics/exercise-1-using-object.md)
-- [Exercise 1 Using Classes](Javascript_Basics/exercise-1-using-classes.md)
-- [Math](Javascript_Basics/Cookies.md)
+- [Variables](JavaScript_Basics/variables.md)
+- [String Operation](JavaScript_Basics/stringOperation.md)
+- [Comparison Operators](JavaScript_Basics/comparisonOperators.md)
+- [Functions](JavaScript_Basics/functions.md)
+- [Arrays](JavaScript_Basics/arrays.md)
+- [Objects](JavaScript_Basics/objects.md)
+- [This](JavaScript_Basics/this.md)
+- [Classes](JavaScript_Basics/classes.md)
+- [Inheritance](JavaScript_Basics/inheritance.md)
+- [Exercise 1](JavaScript_Basics/exercise-1.md)
+- [Exercise 1 Using Object](JavaScript_Basics/exercise-1-using-object.md)
+- [Exercise 1 Using Classes](JavaScript_Basics/exercise-1-using-classes.md)
+- [Math](JavaScript_Basics/Cookies.md)
 
 - JavaScript Advance
 
- - [Arrow Function](Javascript_Advance/arrowFunction.md)
- - [Filtering Arrays](Javascript_Advance/FilteringArray.md)
- - [Destructuring](Javascript_Advance/destructuring.md)
- - [Spread & Rest](Javascript_Advance/spread&rest.md)
- - [Timer Function](Javascript_Advance/timerFunction.md)
- - [Event loop](Javascript_Advance/eventloop.md)
- - [Promises](Javascript_Advance/promises.md)
- - [fs Module](Javascript_Advance/fsModule.md)
- - [Default Values](Javascript_Advance/defaultValues.md)
+ - [Arrow Function](JavaScript_Advance/arrowFunction.md)
+ - [Filtering Arrays](JavaScript_Advance/FilteringArray.md)
+ - [Destructuring](JavaScript_Advance/destructuring.md)
+ - [Spread & Rest](JavaScript_Advance/spread&rest.md)
+ - [Timer Function](JavaScript_Advance/timerFunction.md)
+ - [Event loop](JavaScript_Advance/eventloop.md)
+ - [Promises](JavaScript_Advance/promises.md)
+ - [fs Module](JavaScript_Advance/fsModule.md)
+ - [Default Values](JavaScript_Advance/defaultValues.md)
+ - [Polymorphism](JavaScript_Advance/polymorphism.md)