copy_item_as_json.js

function nbtCompoundToObject(nbt) {
  return Object.fromEntries(
    Array.from(nbt.getKeys())
      .map(key => [key, nbtToObject(nbt.get(key))])
  )
}

function nbtListToArray(nbt) {
  return Array(nbt.length())
    .fill(null)
    .map((_, i) => nbtToObject(nbt.get(i)))
}

function nbtNumberToNumberOrBool(nbt) {
  switch (nbt.getType()) {
    case 1: return nbt.asByte() != 0
    case 2: return nbt.asShort()
    case 3: return nbt.asInt()
    case 4: return nbt.asLong()
    case 5: return nbt.asFloat()
    case 6: return nbt.asDouble()
    default: return nbt.asFloat()
  }
}

function nbtToObject(nbt) {
  switch (true) {
    case nbt == null: return undefined
    case nbt.isNull(): return null
    case nbt.isList(): return nbtListToArray(nbt)
    case nbt.isNumber(): return nbtNumberToNumberOrBool(nbt)
    case nbt.isString(): return nbt.asString()
    case nbt.isCompound(): return nbtCompoundToObject(nbt)
    default:
      return nbt
  }
}

function itemFromSlot(slot) {
  return {
    id: slot.getItemId(),
    count: slot.getCount(),
    category: slot.getCreativeTab(),
    nbt: nbtToObject(slot.getNBT())
  }
}

const shouldCopy = KeyBind.getPressedKeys().contains('key.keyboard.left.control')

if (shouldCopy) {
  event.cancel = true
  const slot = event.getInventory().getSlot(event.slot)
  const message =
    Chat.createTextBuilder()
      .append(`Inspect: ${slot.toString()}`)
      .withShowItemHover(slot)
      .withClickEvent("copy_to_clipboard", JSON.stringify(itemFromSlot(slot)))
      .build()

  Chat.log(message)
}