Here’s the mod I use to spawn specific monsters, I’m not sure if its completely right but it seems to work for the most part.
Selective Spawner Mod:
$("#optionswindow").on("click", '#chicken', function(e) {spawnmonster("chicken", player.x+2, player.y); e.preventDefault();message("Chicken!");});
$("#optionswindow").on("click", '#skeleton', function(e) {spawnmonster("skeleton", player.x+2, player.y); e.preventDefault();message("Skeleton!");});
$("#optionswindow").on("click", '#bogling', function(e) {spawnmonster("bogling", player.x+2, player.y); e.preventDefault();message("Bogling!");});
$("#optionswindow").on("click", '#zombie', function(e) {spawnmonster("zombie", player.x+2, player.y); e.preventDefault();message("Zombie!");});
$("#optionswindow").on("click", '#pirateghost', function(e) {spawnmonster("pirateghost", player.x+1, player.y); e.preventDefault();message("Pirate Ghost!");});
$("#optionswindow").append('<button type="button" id="chicken">Chicken</button>');
$("#optionswindow").append('<button type="button" id="skeleton">Skeleton</button>');
$("#optionswindow").append('<button type="button" id="bogling">Bogling</button>');
$("#optionswindow").append('<button type="button" id="zombie">Zombie</button>');
$("#optionswindow").append('<button type="button" id="pirateghost">Pirate Ghost</button>');