Learning Plan 2 : Variables and Data Types

We're using the JavaScript programming language to learn the basics of programming/development. This is a great language to learn with. All you need to use it is a modern internet browser, like Chrome or Firefox. You can use simple and free programs to write JavaScript called "text editors."

• JavaScript is an interpreted programming language.
• There is a full computer program inside your browser that reads your JavaScript code and runs your code.
• This program is called an "interpreter" and is embedded in browsers. You can't really tell that it is separate from the browser itself.
• You tell the interpreter what to do with a list of instructions. In the beginning of the semester these instructions will be written in HTML files that are your labs and projects.
• For JavaScript to work correctly it has to be put in HTML files correctly. We are going to start by placing our JavaScript code in a special HTML tag:
  

  				<script type="text/javascript">
  				//<!--[CDATA[
  				//<!--
  				// YOUR CODE STARTS AFTER THIS LINE:
  				
  				
  				// END OF YOUR CODE
  				// -->
  				//]]-->
  				</script>
              

• Line 1: The <script> tag is what tells the browser to treat your code as JavaScript.
• Line 2: Start of a CDATA section. This is part of XML and means we can put text in here and modern browsers will leave it alone.
• Line 3: This is an HTML comment to hide our JavaScript code from old browsers that don't understand JavaScript.
• Line 4-7: You put your JavaScript code in here and it will be handed to the JavaScript interpreter by the browser.
• Line 4: This line starts with //. That makes the line a comment that will be ignored by JavaScript.
• Line 8: End of the HTML comment.
• Line 9: End of the CDATA section.
• Here's a peek at coding in JavaScript: Demo: A Peek at JavaScript Coding
• Let's have a lab on this. Here it is: 2.1 Lab 1

In computer programming, there are different levels of rules. Here are the three we are concerned with in this course.

1. Syntax
   • If a computer programming language enforces a rule then we call that rule "syntax". This is the strongest level of rule. You can't break these rules or your program just won't run.
2. Convention
   • If virtually all the users of a programming language all over the world do something the exact same way then that way is called a "convention". The JavaScript language itself doesn't care about these rules. However, if everybody is using the same convention there is good reason for it. If you want to join the ranks of professionals using JavaScript then you need to follow these conventions.
   • In this course, JavaScript won't enforce these rules but your instructor will. Part of the points for projects are on conformance to the course coding standards. Go here to see those: JavaScript Coding Standards for 10-152-310
3. Style
   • There are some ways of structuring our code where there isn't any agreement as to the best way to do it. A large group of programmers will do it one way and another large group will do it another way. When a rule is in this category we call it a "style". Styles are not enforced by JavaScript or the instructor. What is required is that you pick a style for your code and then be consistent. Make sure that you use that style in all your code. We will go over some common styles in class.

Remember those rules about computers? They can't think and they can't figure out what you mean. You have to be very clear and you have to use their language, not yours. Programming languages are very simplistic compared to human languages, but they are very strict. You have to follow the rules of the language that are called its syntax. Here are some of the basic syntax rules of JavaScript.