eg.js

function procCmd(cmd) {
    if (cmd.toLowerCase() == "kill chicken") {
        // 10 refers to the entity TYPE, not an actual entity. It works for spawning entities, but not for referencing them
        
        // We need to cycle through every entity in the world, and kill it if it's a chicken.
        var all_entities = Entity.getAll();
        var i;
        for (i = 0, i < all_entities.length, i++) {
            if (Entity.getEntityTypeId(all_entities[i]) == EntityType.CHICKEN) { // EntityType.CHICKEN is the same as 10
                Entity.setHealth(all_entities[i], 0);
            }
        }
        clientMessage("Killed " + i + " chickens.");
    }
}