Hi,

(function transformRow(source, target, map, log, isUpdate) {

var priprityVal=source.getValue('priority');
if(priprityVal=='High')
{
target.priority ='1';
}
else if(priprityVal=='Medium')
{
target.priority ='2';
}
else
{
target.priority='3';
}

})(source, target, map, log, action==="update");

Thanks,

Dhananjay