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Let's write, execute, and analyze a script that solves the same problem.
The objective of the script is to convert a distance of 2112 paces to a distance in miles where it is given that
Please copy the code from Listing 1 into an html file and open the file in your browser.
| Listing 1 . Convert from paces to miles. |
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>!-- File JavaScript01.html ------------------------------>>html>>body>>script language="JavaScript1.3">var d = 2112 //distance, units = paces
document.write("d = " + d + " paces" + ">/br>")
var d2 = 3000 //distance, units = inchesvar d3 = 100 //distance, units = paces
var f1 = d2/d3 //factor, units = inches/pacedocument.write(
"f1 =" + f1 + " inches/pace" + ">/br>")
//pace*inch/pace = inchvar d = d *f1 //distance, units = inches
document.write("d = " + d + " inches" + ">/br>")
var f2 = 1/12 //factor, units = feet/inchdocument.write(
"f2 = " + f2 + " feet/inch" + ">/br>")
//inch*feet/inch = feetvar d = d *f2 //distance, units = feet
document.write("d = " + d + " feet" + ">/br>")
var f3 = 1/5280 //factor, units = miles/footdocument.write(
"f3 = " + f3 + " miles/foot" + ">/br>")
//feet*mile/feet = milevar d = d *f3 //distance, units = miles
document.write("d = " + d + " mile" + ">/br>")
//Now reverse the process using reciprocals//(pace/inch)*(inch/foot)*(foot/mile) = pace/mile
var f4 =(1/f1)*(1/f2)*(1/f3) //factor, units = paces/miledocument.write(
"f4 = " + f4 + " paces/mile" + ">/br>")
//miles*paces/mile = pacesvar d = d *f4 //distance, units = paces
document.write("d = " + d + " paces" + ">/br>")
document.write("The End")>/script>>/body>>/html> |
Screen output
When you open the html file in your browser, the text shown in Figure 5 should appear in your browser window.
| Figure 5 . Screen output for Listing #1. |
|---|
d = 2112 paces
f1 =30 inches/paced = 63360 inches
f2 = 0.08333333333333333 feet/inchd = 5280 feet
f3 = 0.0001893939393939394 miles/footd = 1 mile
f4 = 2112 paces/miled = 2112 paces
The End |
Discuss the output first
Let's begin our discussion with the screen output shown in Figure 5 and then go back and examine the code that produced that output.
Figure 5 begins with a distance (labeled d ) expressed in units of paces. The value is 2112 paces, which is the distance from your home to your school discussed earlier.
Convert paces to inches
Then Figure 5 shows the conversion factor (labeled f1 ) that can be used to convert a value expressed in paces to a value expressed in inches.
That conversion factor is applied to the original distance producing an output consisting of the same distance expressed in inches instead of paces. Thedistance is now 63360 inches.
Convert from inches to feet
Following that, f2 shows the conversion factor that can be used to convert a value expressed in inches to the same value expressed in feet.
That conversion factor is applied to the current distance value producing an output consisting of the same distance expressed in feet instead of inches. Thedistance is now 5280 feet.
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