A plugin that makes it so that when a player executes a command they have to have some elytras on

function getElytraType(player){
   var itemInHand = player.getInventory().getItemInHand()
   if(itemInHand.getItemMeta().getDisplayName() == "Elytra"){
      return "Elytra"
   }else if(itemInHand.getItemMeta().getDisplayName() == "Rocket Boots"){
      return "Rocket Boots"
   }else{
      return "no elytra"
   }
}