debug.getupvalue Synchronous

Read the value captured in one upvalue slot of a Luau function. It is useful for checking the state a closure carries without calling it.

Syntax

Luau

debug.getupvalue(target: Function | number, index: number) -> any

Parameters

Function parameters
Parameter	Type	Description
`target`	`Function \| number`	A Luau function or visible stack level.
`index`	`number`	One-based upvalue slot.

any

The captured value.

Luau

local count = 0
local function nextCount() count += 1; return count end
print(debug.getupvalue(nextCount, 1)) -- 0