Stopwatch in Roblox Lua using a while loop - time

Question

I am making a Roblox game and I want it to have a stopwatch. The stopwatch works, but it counts very slowly for some reason.
Here's my ScreenGui in StarterGui:
Here's the code inside the LocalScript:
local timer = script.Parent.Timer
local tms = 00
local ts = 00
local tm = 00
local tt
local tts
local y = 0
local whichtower = game.Players.LocalPlayer:FindFirstChild("WhichTower")
while true do
wait(0.01)
if whichtower.Value == "" then
tms = 00
ts = 00
tm = 00
tts = 0
else
tms = tms + 1
if tms == 100 then
ts = ts + 1
tms = 0
tts = tts + 1
if ts == 60 then
tm = tm + 1
ts = 0
end
end
tt = tostring(tm)..":"..tostring(ts)..":"..tostring(tms)
timer.Text = tt
game.Players.LocalPlayer:FindFirstChild("Time").Value = tt
end
end

Answer 1

The arbitrary wait() and loop is a possible cause of timing issues, although I can't see anything specific that might be slowing it down. Are you sure that :FindFirstChild on WHichTower is always returning results? Add a print statement there, so your debug window has a constant stream of values, and you can confirm if it's finding a suitable tower.
Also, you are only updating the text if there's a Tower; for the code where you set the values to 0, there's no timer.Text update.
But if you don't think that's the issue:
I'd try put your code in a Heartbeat function, called regularly and tied to the refresh rate (I think). Then you don't need the while loop, nor the wait() commands. The Heartbeat only runs as fast as the refresh rate, therefore, there's no point trying to running anything quicker than that because the screen won't update.
local lPlayers = game:GetService("Players")
local lRunSvc = game:GetService("RunService")
local function onPlayerAdded(pPlayer) -- pPlayer (variable name is up to you) is the ref to the joined player.
print(pPlayer.Name .. " joined the game.")
lRunSvc.Heartbeat:Connect(function()
print("whichtower.value is:" .. whichtower.Value) -- View prints in the Output console
if whichtower.Value == "" then
tms = 00
ts = 00
tm = 00
tts = 0
else
tms = tms + 1
if tms == 100 then
ts = ts + 1
tms = 0
tts = tts + 1
if ts == 60 then
tm = tm + 1
ts = 0
end
end
tt = tostring(tm)..":"..tostring(ts)..":"..tostring(tms)
timer.Text = tt
game.Players.LocalPlayer:FindFirstChild("Time").Value = tt
end
end)
end
lPlayers.PlayerAdded:Connect(onPlayerAdded) -- This is called when a player joins

Answer 2

Just as Vexen Crabtree has pointed out, the time that wait() will actually pause a script is based on a system clock's best guess of how much time has passed. Rather than counting up the milliseconds, a more reliable method for calculating passed time is to use the tick() function.
tick() will give you the current epoch time, which is the number of milliseconds that have passed since January 1st, 1970.
So, if you know a starting time, you can subtract it from the current time and get the number of milliseconds that have passed. This method doesn't rely on loop timings and will give a more accurate measure of the actual time that has passed. The amount of time that you chose with wait() will only reflect the speed at which the value will be updated.
local timer = script.Parent.Timer
local whichtower = game.Players.LocalPlayer:FindFirstChild("WhichTower")
local playerTime = game.Players.LocalPlayer:FindFirstChild("Time")
local startingTime = 0
local isTiming = false
-- attach a listener to know when to start the clock
whichTower.Changed:Connect(function(newValue)
-- reset the clock to zero when the value is empty
isTiming = newValue ~= ""
if not isTiming then
startingTime = 0
else
-- start the clock!
startingTime = tick()
end
end)
local refreshTime = 0.01
while true do
wait(refreshTime)
if isTiming then
-- calculate the time that has passed
local ms = tick() - startingTime
-- calculate how many minutes have passed
local tm = ms - (ms % (60 * 1000))
ms = ms - tm
tm = tm / 1000
-- calculate how many seconds have passed
local ts = ms - (ms % 1000)
ms = ms - ts
ts = ts / 1000
-- format the remainder
local tms = ms / 1000
if #tostring(tms) > 2 then
tms = string.sub(tostring(tms), 3)
else
tms = "0"
end
-- format the time into mm:ss.ss ex) 123:01.123
local tt = string.format("%.2d:%.2d.%s", tm, ts, tms)
timer.Text = tt
playerTime.Value = tt
end
end

Answer 3

I have figured it out using a different set of code. Roblox limits the wait parameters to a minimum of 0.03 seconds, so that is why my previous code was not working.