// calculate the difference btw new and old RGB values
// Analysis
var newRed = 255;
var oldRed = 0;
var newGreen = 0;
var oldGreen = 0;
var oldBlue = 255;
var newBlue = 155;
var difRed = newRed - oldRed;
var difGreen = newGreen - oldGreen;
var difBlue = newBlue - oldBlue;
document.writeln("oldRed: " + oldRed + "<br>newRed: " + newRed);
document.writeln("<br>difRed: " + difRed);
document.writeln("<p>oldGreen: " + oldGreen + "<br>newGreen: " + newGreen);
document.writeln("<br>difGreen: " + difGreen);
document.writeln("<p>oldBlue: " + oldBlue + "<br>newBlue: " + newBlue);
document.writeln("<br>difBlue: " + difBlue);
This code fragment creates 6 variables to hold the new and old RGB values. The test values represent the three possible scenarios - no change, positive change, and negative change. Three more variables are created to hold the differences between the values. Each old RGB value is subtracted from the new RGB value, and the results are written to the screen.