Added comments, removed unused variables.

Signed-off-by: npalomba <nicola.palomba@studenti.galileilivorno.gov.it>

js/_checkerboard.js

@@ -1,13 +1,15 @@
+// This script contains all the functions used to manage the checkboard
+
+// Setting current colour (each square has a different colour
 var currentColor = firstCheckerBoardColor;
+// Saving number of squares filled until now
 var nSquaresFilled = 0;
 
-/* TODO add check for canvas dimentions (right now negative values can be inserted and a canvas will be generated, it is just
-    necessary to add a conversion from negative to positive values.
- */
-
 function fillCheckerboard() {
+    // Getting checkerboard context
     var context = checkerBoard.context;
 
+    // Cycling through the canvas (using it as a matrix)
     for (var i=0; i<canvasSize[0] / checkerBoardSquareSize; i++) {
         nSquaresFilled = 0;
 
@@ -15,6 +17,7 @@ function fillCheckerboard() {
             var rectX;
             var rectY;
 
+            // Managing the not perfect squares (the ones at the sides if the canvas' sizes are not powers of checkerBoardSquareSize
             if (i * checkerBoardSquareSize < canvasSize[0]) {
                 rectX = i * checkerBoardSquareSize;
             }
@@ -29,20 +32,24 @@ function fillCheckerboard() {
                 rectY = canvasSize[1];
             }
 
+            // Selecting the colour
             context.fillStyle = currentColor;
             context.fillRect(rectX, rectY, checkerBoardSquareSize, checkerBoardSquareSize);
 
+            // Changing colour
             changeCheckerboardColor();
 
             nSquaresFilled++;
         }
 
+        // If the number of filled squares was even, I change colour for the next column
         if ((nSquaresFilled % 2) == 0) {
             changeCheckerboardColor();
         }
     }
 }
 
+// Simply switches the checkerboard colour
 function changeCheckerboardColor(isVertical) {
     if (currentColor == firstCheckerBoardColor) {
         currentColor = secondCheckerBoardColor;