Prototype Object.pptx
- 2. JAVASCRIPT PROTOTYPE OBJECT JavaScript is a prototype-based language that facilitates the objects to acquire properties and features from one another. Here, each object contains a prototype object. In JavaScript, whenever a function is created the prototype property is added to that function automatically. This property is a prototype object that holds a constructor property.
- 3. JAVASCRIPT PROTOTYPE OBJECT Syntax: ClassName.prototype.methodName What is the requirement of a prototype object? Whenever an object is created in JavaScript, its corresponding functions are loaded into memory. So, a new copy of the function is created on each object creation. In a prototype-based approach, all the objects share the same function. This ignores the requirement of creating a new copy of function for each object. Thus, the functions are loaded once into the memory.
- 4. JAVASCRIPT PROTOTYPE OBJECT Prototype Chaining In JavaScript, each object contains a prototype object that acquires properties and methods from it. Again an object's prototype object may contain a prototype object that also acquires properties and methods, and so on. It can be seen as prototype chaining.
- 5. JavaScript Prototype Object Example 2 Let's see an example to add a new method to the constructor function. <!DOCTYPE html> <html> <body> <script> function Employee(firstName,lastName) { this.firstName=firstName; this.lastName=lastName; } Employee.prototype.company="Javatpoint" var employee1=new Employee("Martin","Roy"); var employee2=new Employee("Duke", "William"); document.writeln(employee1.firstName+" "+employee1.lastName+" "+employee1.company+"<br>"); document.writeln(employee2.firstName+" "+employee2.lastName+" "+employee2.company); </script> </body> </html>
- 6. JavaScript Constructor Method A JavaScript constructor method is a special type of method which is used to initialize and create an object. It is called when memory is allocated for an object. Points to remember: o The constructor keyword is used to declare a constructor method. o The class can contain one constructor method only. o JavaScript allows us to use parent class constructor through super keyword.
- 7. Constructor Method Example Let's see a simple example of a constructor method. <!DOCTYPE html> <html> <body> <script> class Employee { constructor() { this.id=101; this.name = "Martin Roy"; } } var emp = new Employee(); document.writeln(emp.id+" "+emp.name); </script> </body> </html>
- 8. Constructor Method Example: super keyword The super keyword is used to call the parent class constructor. Let's see an example. <!DOCTYPE html> <html> <body> <script> class CompanyName { constructor() { this.company="trizymartzy"; } } class Employee extends CompanyName { constructor(id,name) { super(); this.id=id; this.name=name; } } var emp = new Employee(1,"John"); document.writeln(emp.id+" "+emp.name+" "+emp.company); </script> </body> </html>
- 9. What have you learned?
- 10. Activity 01: Perform the codes for: 1.Prototype object; 2.Constructor method;and 3. Super keyword Activity 1: Rubrics Points Description 10 The student successfully executes the program without guidance or supervision. 9 The student successfully executes the program with very little supervision and guidance. 8 The student successfully executes the program with moderate supervision andguidance. 7 The student was not able to execute the program but shows eagerness to accomplishthe activity. 5 The student was not able to execute the program due to lack of interest in the activity.
- 11. Thank You!