We can order a catalog item from a script. Before that, we need to design the catalog item and make sure all necessary variables are ready.

var cartId = GlideGuid.generate(null);
var cart = new Cart(cartId);
 //add your requested item to the cart by sys_id of the catalog item
var item = cart.addItem('item_sys_id', 1);

//fill in the variables on the request item form
cart.setVariable(item,"u_requested_for", "e80edd6edbec6bc097275e25ca9619a4"); 
cart.setVariable(item,"contact_number", "0");
cart.setVariable(item,"assignment_group", "87ec1c342b2e71406c487fb5a8da1524"); 
cart.setVariable(item,"application_service", "cdedfbcedb0f9744c291c170ba9619a7");
cart.setVariable(item,"short_description", email.subject);
cart.setVariable(item,"description", email.body_text);
var rc = cart.placeOrder();