src/geometry.js
function(j, coordSystem, size) {
    if ("aa" === coordSystem) {
	return String.fromCharCode(CODE_a + --j);
    }
    else { // "A1" (default)
	return (size - --j).toString();
    }
}
function(j, coordSystem, size) {
    if ("aa" === coordSystem) {
	return String.fromCharCode(CODE_a + --j);
    }
    else { // "A1" (default)
	return (size - --j).toString();
    }
}
function ( j , coordSystem , size ) { if ( "aa" === coordSystem ) { return String . fromCharCode ( CODE_a + -- j ) ; } else { // "A1" (default) return ( size - -- j ) . toString ( ) ; } }
Defines vertical label.

@param {number} j index of row
@param {string} coordSystem ("A1" or "aa")
@param {number} size the grid base (9, 13, 19)
@returns {string}
Defines vertical label .