JavaScript object programming

Object-Oriented Java Script Object-Oriented JavaScript JavaScript 2 Objectives • Study object-oriented programming • Learn about the built-in JavaScript objects • Work with the Array, Date, Math, and Number objects • Define custom JavaScript objects JavaScript 3 Introduction to Object-Oriented Programming • Object-oriented programming allows you to reuse code without having to copy or recreate it • You already have some experience with object-oriented programming after working with browser objects(window, Document, Form objects) JavaScript 4 Reusable Software • Object-oriented programming (OOP): – Refers to the creation of reusable software objects that can be easily incorporated into multiple programs • Object: – Specifically refers to programming code and data that can be treated as an individual unit or component JavaScript 5 Reusable Software (Cont.) • Data: – Refers to information contained within variables or other types of storage structures • Objects can range from simple controls such as a button, to entire programs such as a database application – In a retail sales program, you could refer to all the code that calculates the sales total as a single object. – You could reuse the object over and over again in the same program by typing the object name. JavaScript 6 Reusable Software (Cont.) • Popular object-oriented programming languages include C++, Java, and Visual Basic • Using any of these or other object-oriented languages: – Programmers can create objects themselves or use objects created by other programmers JavaScript 7 Encapsulation • Objects are encapsulated: – All code and required data are contained within the object itself • Encapsulation: – Places code inside what programmers like to call a “black box” – When an object is encapsulated, you cannot see “inside” it—all internal workings are hidden JavaScript 8 Encapsulation (Cont.) • The code (methods and statements) and data (variables and constants) contained in an encapsulated object are accessed through an interface • Interface: – Represents elements required for a source program to communicate with an object • Interface elements required to access a Payroll object might be a method named calcNetPay() JavaScript 9 Encapsulation (Cont.) • The principal of information hiding states that: – Any class members that other programmers do not need to access or know about should be hidden • Think of a calculator as an object, the interface is the keypad. – You do not need to know or see the inner workings of the calculator to operate it JavaScript 10 Encapsulation (Cont.) • Encapsulation prevents other programmers from: – Accidentally introducing a bug into a program – Stealing the code and claiming it as their own [...]... not a true object- oriented programming language: – Base objects in your programs on built-in JavaScript classes such as the Array and Date objects – However, you cannot create your own classes in JavaScript – You can define your own custom objects using a constructor function JavaScript 30 Custom JavaScript Objects • A Constructor function used as the basis for a custom object • JavaScript objects inherit... limitations in the JavaScript language JavaScript 23 Number Class Methods JavaScript 24 Number Class Properties JavaScript 25 Math Class • The Math class contains methods and properties for performing mathematical calculations in your programs JavaScript 26 Math Class Methods JavaScript 27 Math Class Methods (Cont.) JavaScript 28 Math Class Properties JavaScript 29 Custom JavaScript Objects • JavaScript is... class JavaScript 13 Classes (Cont.) • Class names in traditional object- oriented programming usually begin with an uppercase letter This convention is also followed in JavaScript JavaScript 14 Built-in JavaScript Classes JavaScript 15 Instantiating an Object • You can use some of the built-in JavaScript objects directly in your code – document.write(“The value of PI is “ + Math.PI); • Other objects... (Cont.) JavaScript 11 Classes • In object- oriented programming: – Code, methods, attributes, and other information that make up an object are organized into classes • Class: – Template, or blueprint, that serves as the basis for new objects • Instance: – Object that has been created from an existing class • Called instantiating the object JavaScript 12 Classes (Cont.) • A particular instance of an object. .. instantiate a new object – var studentList = new Array() JavaScript 16 Garbage Collection • When you instantiate a new object, you are reserving memory • Refers to cleaning up, or reclaiming, memory that is reserved by a program • JavaScript knows when a program no longer needs a variable or object – Automatically cleans up the memory JavaScript 17 Array Class • The Array class creates new array objects •... using the following syntax: array_name.length; JavaScript 20 Date Class • Contains methods and properties for manipulating the date and time • The Date object allows you to use the current date and time in your JavaScript programs • You create a new instance of the Date class using the syntax var dateObject = new Date(); JavaScript 21 Date Class (Cont.) JavaScript 22 Number Class • Contains methods... the constructor function on which they are based • Any JavaScript function can serve as a constructor JavaScript 31 Custom JavaScript Objects • The following code defines a function named candyOrder() with three paramaters that can serve as a construction function function candyOrder(customer, type, boxes){ … } var valentinesDay = new candyOrder(); JavaScript 32 Properties • To add a property to a constructor... statement to the function body that uses the this keyword with the following syntax: • this.property_name = value; – In the case of a custom JavaScript object, the this keyword refers to the object that calls the constructor function JavaScript 33 Properties JavaScript 34 Methods • You can create a function that will be used as an object method: – By referring to any object properties using the this reference JavaScript 35 Methods object called BankAccount that contains methods and properties that you might use to record transactions associated with a checking or savings account • The BankAccount object is created from a BankAccount class • To use the BankAccount class you create an instance of the class • A particular instance of an object inherits its methods and properties from a class • The BankAccout object inherits . Object- Oriented Java Script Object- Oriented JavaScript JavaScript 2 Objectives • Study object- oriented programming • Learn about the built-in JavaScript objects • Work with. with the Array, Date, Math, and Number objects • Define custom JavaScript objects JavaScript 3 Introduction to Object- Oriented Programming • Object- oriented programming allows you to reuse code. have some experience with object- oriented programming after working with browser objects(window, Document, Form objects) JavaScript 4 Reusable Software • Object- oriented programming (OOP): – Refers