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Tutorial 1: Introduction to JavaScript

Tutorial 1: Introduction to JavaScript. Section A: Programming, HTML, and JavaScript. Objectives. In this section, we will learn: About the World Wide Web What JavaScript is used for About Hypertext Markup Language How to create an HTML document About the JavaScript programming language

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Tutorial 1: Introduction to JavaScript

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  1. Tutorial 1: Introduction to JavaScript Section A: Programming, HTML, and JavaScript

  2. Objectives • In this section, we will learn: • About the World Wide Web • What JavaScript is used for • About Hypertext Markup Language • How to create an HTML document • About the JavaScript programming language • About logic and debugging

  3. The World Wide Web • JavaScript lives and works within Web pages on the World Wide Web • World Wide Web (the “Web”) was created in 1989 at the European Laboratory for Particle Physics in Geneva, Switzerland

  4. The World Wide Web • Documents are located and opened using hypertext links, which contain a reference to a specific document • What is HTML? • Hypertext Markup Language (HTML) is a simple language used to design Web pages

  5. The World Wide Web • What’s a Web browser? • Web browser is a program that displays HTML documents on your computer screen • Hypertext Transfer Protocol (HTTP) manages hypertext links used to navigate the Web

  6. The World Wide Web • What’s a Domain Name? • Domain name is a unique address used for identifying a computer, often a Web server, on the Internet • Why do I ask so damn many questions? • A: To annoy the living Hell out of you

  7. The World Wide Web • What does a Domain Name consist of? • Domain name consists of two parts separated by a period: • Usually composed of text that identifies a person or organization • Identifies the type of institution or organization • For example, dsu.edu

  8. Sample URL

  9. JavaScript’s Role on the Web • The main purpose of HTML is to tell a browser how the document should appear • JavaScript brings HTML to life and makes Web pages dynamic • Dynamic basically means using the power of JavaScript to generate Web content on-the-fly

  10. JavaScript’s Role on the Web • Use JavaScript to change the contents of a Web page after it has been rendered by a browser • JavaScript is used for many different purposes, including advertising and entertainment

  11. Hypertext Markup Language • HTML documents must be text documents that contain formatting instructions, called tags, along with the text that has to be displayed on a Web page • What 3 tags are common to every HTML document?

  12. Hypertext Markup Language • HTML tags range from formatting commands that boldface and italicize text to controls that allow user input • Which HTML tags do that? • Many tags also have attributes that determine how they look, function, etc. • <FONT FACE=“ARIAL” SIZE=“10”>

  13. Hypertext Markup Language • HTML documents must have a file extension of .html or .htm • Assembling and formatting an HTML document is called parsing or rendering

  14. Common HTML Tags

  15. Hypertext Markup Language • Two important HTML tags are the <HEAD> and <BODY> • The <HEAD> tag is placed at the start of an HTML document • When a Web browser renders an HTML document, it ignores non-printing characters and only recognizes HTML tags and text included in the final document

  16. HTML Tags Placed Within the <HEAD>…<HEAD> Tag Pair

  17. <BODY> Tag Attributes

  18. Creating an HTML Document • Since HTML documents are text files, you can create them in any text editor such as ConTEXT, NotePad, WordPad, or any word-processing program • NOTE: HTML documents displayed in Internet Explorer can appear differently in Navigator

  19. The JavaScript Programming Language • JavaScript is a scripting language • Scripting language refers to programming languages that are executed by an interpreter from within a Web browser • What’s the diff between an interpreted language and a compiled language?

  20. The JavaScript Programming Language • Interpreter translates programming code into an executable format each time the program is run • Scripting engine is an interpreter that is part of the Web browser • Scripting host is a web browser that contains a scripting engine

  21. The JavaScript Programming Language • JavaScript language was first introduced in Navigator and was originally called LiveScript • JavaScript is available in two formats: client-side and server-side • What’s that mean?

  22. The JavaScript Programming Language • The standardized client-side JavaScript is the format available to HTML pages displayed in Web browsers • Server-side JavaScript is proprietary and vendor-specific

  23. Relationship of Client-Side and Server-Side JavaScript

  24. Logic and Debugging • JavaScript has its own syntax, or rules of the language • Logic underlying any program involves executing the various parts of the program in correct order to produce desired results

  25. Logic and Debugging • Any error in a program that causes it to function incorrectly is called a bug • Debugging describes the act of tracing and resolving errors in a program. Term coined by Grace Murray Hopper, who was instrumental in developing the COBOL programming language • She’s believed to have been drunk at the time

  26. Section A: Chapter Summary • Hypertext Markup Language (HTML) is a simple protocol used to design Web pages that appear on the World Wide Web • The World Wide Web is driven by Hypertext Transfer Protocol (HTTP), which manages hypertext links that are used to navigate the Web

  27. Section A: Chapter Summary • Every Web document has a unique address known as a Uniform Resource Locator (URL) • JavaScript brings HTML to life and makes Web pages dynamic, turning them into applications

  28. Section A: Chapter Summary • HTML documents must be text documents that contain formatting instructions, called tags, along with the text that is to be displayed on Web page • HTML tags range from formatting commands to controls that allow user input, to tags that allow the display of graphic images and other objects

  29. Section A: Chapter Summary • An interpreter translates programming code into an executable format each time the program is run--one line at a time • JavaScript is an interpreted programming language

  30. Section A: Chapter Summary • A scripting engine is an interpreter that is part of the Web browser which contains a scripting host • All programming languages, including JavaScript, have their own syntax, or rules of the language

  31. Section A: Chapter Summary • The logic behind any program involves executing the various parts of the program in the correct order to produce the desired results • Grace Murray Hopper, who was instrumental in developing COBOL, drank like a fish

  32. Tutorial 1: Introduction to JavaScript Section B: A First JavaScript Program

  33. Objectives • In this section, we will learn: • About the <Script> tag • How to create a JavaScript source file • How to add comments to a JavaScript program • How to hide JavaScript from incompatible browsers • About placing JavaScript in HEAD or BODY section of HTML documents

  34. The <SCRIPT> Tag • Statements that make up a JavaScript program in an HTML document are contained between the <SCRIPT>…</SCRIPT> tag pairs • The <SCRIPT> tag is used to notify the Web browser that commands following it need to be interpreted by a scripting engine

  35. The <SCRIPT> Tag • The language attribute of the <SCRIPT> tag tells the browser which scripting language and version is being used

  36. JavaScript Versions Supported by Navigator

  37. The <SCRIPT> Tag • An object is programming code and data that can be treated as an individual unit or component • Before we go any further, who can explain objects, properties, and methods? • Individual lines in a programming language are called statements

  38. The <SCRIPT> Tag • Groups of related statements associated with an object are called methods • To execute, or call, an object’s methods, append the method to the object with a period, and include any required arguments or parameters between parentheses

  39. The <SCRIPT> Tag • An argument is any type of information that can be passed to a method • HINT: It’s the stuff in parentheses • The write () and writeln() methods require a text string as an argument

  40. The <SCRIPT> Tag • Text string, or literal string, is text that is contained within double quotation marks • The only difference between the write() and writeln() methods is that the writeln () method adds a carriage return after the line of text

  41. Script Using Writeln() Method

  42. Output of Writeln() Script

  43. Why Did They Puke?

  44. Creating a JavaScript Document • Reference page 24 of the textbook

  45. Page 24 Script in IE • The MyFirstJavaScript.html file in all its glory

  46. Creating a JavaScript Source File • JavaScript is often incorporated directly into an HTML document • Can also save JavaScript code in an external file called a source file with file extension .js • The SRC attribute accepts a text string that specifies the URL or directory location of a JavaScript source file

  47. Creating a JavaScript Source File • JavaScript source files cannot include HTML tags – you will get an error • If JavaScript code intended for use in HTML document is fairly short, usually easier to include the code in an HTML document. • For longer JavaScript code, it is easier to include the code in a .js source file

  48. Creating a JavaScript Source File • Why would you may want to use .js source files instead of adding code to HTML? • Your HTML document will be neater • The JavaScript code can be shared among multiple HTML documents • JavaScript source files hide JavaScript code from incompatible browsers

  49. Creating a JavaScript Source File • You can use a combination of embedded JavaScript code and source files in your HTML document

  50. Adding Comments to a JavaScript Program • Comments are nonprinting lines that you place in code to contain various types of remarks. For example,name of program, your name, date created, and expletives • Line comments are created by adding two slashes // before the text • Block comments span multiple lines and are created by adding /* to the first line to be included in the block

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