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Screen output
The text shown in Figure 9 should appear in your browser window when the html file is opened in your browser.
| Figure 9 . Screen output for Listing #4. |
|---|
Start Script
Platform velocity magnitude = 3.70 miles/hourPlatform velocity angle = 22.50 degrees
Man velocity magnitude = 4.83 miles/hourMan velocity angle = 45.00 degrees
End Script |
Analysis of the code
The velocity of the platform relative to the ground is the vector sum of the ship's velocity and the velocity of the platform relative to the ship. The man's velocity is the vector sum of theplatform's velocity relative to the ground and the man's velocity relative to the platform.
Listing 4 begins with copies of the getAngle function and the vectorSum function, which I have already explained. This discussion begins at the commentthat reads "Main body of script begins here."
The main body of the script
The main body begins with the declaration and initialization of six variables whose contents represent the magnitude and the angle of the ship, theplatform, and the man.
Add the first two vectors
The vectorSum function is called to add the ship's velocity vector (relative to the ground) and the platform'svelocity vector (relative to the ship). The resultant vector produced by adding those two vectors is stored in the array-object variable named platformVel for use later. This is the platform's velocity vector relative to the ground.
Add the man's vector to the sum
Then the vectorSum function is called again to add the platform's velocity vector (relative to the ground) andthe man's velocity vector (relative to the platform). Note that the two values stored in the platformVel array object are extracted and passed as parameters to the vectorSum function.
The resultant vector produced by that addition is saved in the array-object variable named manVel . This is the man's velocity vector relative to the ground.
Display the results
Finally, the method named document.write is called four times in succession to extract and print the four values stored in the two array objects, producing thetext output shown in Figure 9 .
I encourage you to run the scripts that I have presented in this lesson to confirm that you get the same results. Copy the code for each script into atext file with an extension of html. Then open that file in your browser. Experiment with the code, making changes, and observing the results of your changes. Makecertain that you can explain why your changes behave as they do.
This section contains a variety of miscellaneous information.
Financial : Although the Connexions site makes it possible for you to download a PDFfile for this module at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should be aware thatsome of the HTML elements in this module may not translate well into PDF.
I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.
In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.comshowing me as the author. I neither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, pleasebe aware that it is a copy of a module that is freely available on cnx.org and that it was made and published without my prior knowledge.
Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.
-end-
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