BackGammon board mappings in JS

run.js

/*
  Red 0 == Black 25
  Red 1 == Black 24 == R1
  Black 1 == Red 24 == B1
  Red 12 == Black 13 == R12
  Black 12 == Red 13 == B12
*/

// map a color place to a bpard position
var x = function(pos, color) {
	var mapped = undefined;
	if(pos < 0) pos = 0;
	if(pos > 25) pos = 25;
	if (color == "Red") {
		if (pos <= 12) {
			mapped = "R" + pos;
		} else {
			mapped = "B" + (25 - pos)
		}
	} else if (color == "Black") {
		if (pos <= 12) {
			mapped = "B" + pos;
		} else {
			mapped = "R" + (25 - pos)
		}
	}
	return mapped;
};

// map a board position to a color place
var y = function(pos, color) {
	var mapped = undefined;
	var redPos = 0;
	var split = [pos.slice(0,1), parseInt(pos.slice(1))];
	if (split[1] != NaN) {
		if (split[0] == "R") {
			redPos = split[1];
		} else if (split[0] == "B") {
			redPos = 25 - split[1];
		}
		mapped = redPos;
		if (color == "Black") {
			mapped = 25 - redPos;
		}
	}
	return mapped;
};

console.log(x(0,  "Red"));
console.log(x(5,  "Red"));
console.log(x(21, "Red"));
console.log(x(24, "Red"));
console.log(x(27, "Red"));

console.log("     ");

console.log(x(0,  "Black"));
console.log(x(5,  "Black"));
console.log(x(21, "Black"));
console.log(x(24, "Black"));
console.log(x(27, "Black"));

console.log("     ");

console.log(y("R4", "Black"));
console.log(y("R21", "Red"));
console.log(y("B4", "Red"));
console.log(y("B0", "Red"));