Final Code - HTML5 with Visual Studio 2012 - page 377

// Compute the x and y coordinates
var xStart = parseInt(startPos.substr(0, 1));
var yStart = parseInt(startPos.substr(1, 1));
var xEnd = parseInt(endPos.substr(0, 1));
var yEnd = parseInt(endPos.substr(1, 1));
switch (prefix) {
// For white pieces...
case "w":
if (yEnd <= yStart)
return false; // Can't move backwards
break;
// For black pieces...
case "b":
if (yEnd >= yStart)
return false; // Can't move backwards
break;
}
// These rule apply to all pieces
if (yStart === yEnd || xStart === xEnd)
return false; // Move must be diagonal
if (Math.abs(yEnd - yStart) > 2 || Math.abs(xEnd - xStart) > 2)
return false; // Can't move more than two spaces
if (Math.abs(xEnd - xStart) === 1 && jumpOnly)
return false; // Only jumps are allowed
var jumped = false;
// If moving two spaces, find the square that is jumped
if (Math.abs(xEnd - xStart) === 2) {
var pos = ((xStart + xEnd) / 2).toString() +
((yStart + yEnd) / 2).toString();
var div = document.getElementById(pos);
if (div.childElementCount === 0)
return false; // Can't jump an empty square
var img = div.children[0];
if (img.id.substr(0, 1).toLowerCase() === prefix.toLowerCase())
return false; // Can't jump a piece of the same color
// If this function is called from the drop event
// Remove the jumped piece
if (drop) {
div.removeChild(img);
jumped = true;
}
}
// Set the draggable attributes so the next player can take a turn.
if (drop) {
enableNextPlayer(source);