var item = <item:minecraft:bedrock>;  // as IItemStack
var registryName = item.registryName; // as ResourceLocation
var namespace = registryName.namespace; // "minecraft" as string
var path = registryName.path; // "bedrock" as string
var registryNameAsString = registryName.toString(); // "minecraft:bedrock" as string

var commandString = item.commandString; //"<item:minecraft:bedrock>" as string