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Dr. Weiss has asked for your help in constructing an online planisphere for his Web site.
He has created 24 different sky chart image files, named sky0.jpg through sky23.jpg ,
that represent 24 different rotations of the nighttime sky. He has also created an image
containing a transparent window through which a user can view a selected sky chart. A
preview of the completed Web page is shown in Figure 10-37.
Figure 10-37
skyWeb planisphere page
Dr. Weiss has designed the page layout. He needs your help in creating JavaScript code
to display the current date and time and to display the correct sky chart for that date and
time. To do this, you've been provided with two functions:
• The showDateTime() function returns the current date and time in the text string
MonthƒDay Year hour : minute ƒam/pmƒ
where Month is the name of the current month, Day is the current day, Year is the
current year, hour is the current hour, minute is the current minute, and am/pm
changes based on the current time.
• The getMap() function returns a number from 0 to 23. The number matches the num-
ber of the sky map image to show based on the current date and time.
Both functions have been placed in an external JavaScript file named datetime.js .
Complete the following:
1. Use your text editor to open the skymaptxt.htm file from the tutorial.10\case1 folder
included with your Data Files. Enter your name and the date in the comment sec-
tion of the file. Save the file as skymap.htm in the same folder.
2. Directly below the link element in the head section, insert a script element
accessing the datetime.js file.
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