CMSC 104, Fall 2009

Homework 3

Your First JavaScript Program

Out: Tuesday, October 20, 2009
Due: Tuesday, October 27, 2009 by 11:59 p.m.

Note: No late projects will be accepted.

The Objective

To learn to create and run JavaScript programs
To become familiar with syntax error messages generated by the JavaScript error console.

The Task

Before you begin working on the assignment, you must set up your account so that no one else can see your Web page while you are working on it. You will only be able to access your page by typing in a username and password. The only people who will be able to access your page are you, me and the graders for the class. You *must* do this step before you begin working on your page. Note that when you type in your password for the script nothing will show up on the screen, just type it and hit enter. Type the following command at the linux prompt:

linux2[12]% /afs/umbc.edu/users/o/r/ordopa1/pub/setup104

You should see something similar to the following:

linux2[12]% /afs/umbc.edu/users/o/r/ordopa1/pub/setup104
Creating new directory: /afs/umbc.edu/users/c/m/cmsc/pub/access
Using exising directory: /afs/umbc.edu/users/c/m/cmsc/pub/www
Using exising directory: /afs/umbc.edu/users/c/m/cmsc/pub/www/cs104
Using exising directory: /afs/umbc.edu/users/c/m/cmsc/pub/www/cs104/hw3
Using exising directory: /afs/umbc.edu/users/c/m/cmsc/pub/www/cs104/proj1
Using exising directory: /afs/umbc.edu/users/c/m/cmsc/pub/www/cs104/proj2
Using exising directory: /afs/umbc.edu/users/c/m/cmsc/pub/www/cs104/proj3
Using exising directory: /afs/umbc.edu/users/c/m/cmsc/pub/www/cs104/proj4

*********************************************************************
* Please enter a password other than your myUMBC/GL password below. *
*  This will be the password you need to access your pages online.  *
*********************************************************************

Creating new password file
New password:
Re-type new password:
Adding password for user cmsc
linux2[13]%

After you run the setup script, you will be asked for a password when you eventually look at your Web page for the assignment in the Web browser.
For the first part of the assignment, you must complete the program attached to this sheet (to be distributed in class) by filling in the blanks where pieces of code are missing.

Look carefully through the entire program before starting to fill in the blanks. It is more straightforward than you think. For example, we actually refer to specific variable names later on in the body, so you don't really have a choice in the naming of the variables declared in the "var ________" lines, near the top of the program.
Use common sense; for example, the test in the "else if" part could syntactically be exactly the same as in the first "if", but that is obviously not what we want!

After filling in the blanks, you are ready to move on to the second part of the assignment.
- Change into your hw3 directory. (cd ../pub/www/cs104/hw3).
- Use xemacs (xemacs hw3.html) to type in the JavaScript program. You should type the program in INCREMENTALLY!! Type it in EXACTLY AS SHOWN, including all spacing and indentation. Some exceptions:
  1. Insert YOUR name as the author.
  2. Insert YOUR username.
  3. Insert a heading of your choice on the page where it says "Heading for Your Page."
  4. You may add a <style>...</style> section to the head section of the page if you'd like to change the colors, fonts, etc.
- The program must be called hw3.html. It should be located in your pub/www/cs104/hw3/ directory. The grader will access your page directly from the given directory.

Using the JavaScript Error Console

The JavaScript error console will help you find errors in your program. To run the error console in Firefox, go to Tools->Error Console. It will bring up a separate window containing the error console. You should use the Clear button to clear the error console and then refresh your web page. If there are any problems with your JavaScript code, they should show up in the error console.

Sample Run

The URL for your page will be http://userpages.umbc.edu/~username/cs104/hw3/hw3.html, where username is your GL/myUMBC username. You should refresh the page several times and run the program with different sets of values. You can assume that the user will only enter numbers as input. Here are some sample screenshots of the program:

User entering first number

User entering second number

Final results page

CMSC104