how do you check if a part in the character exists?

To ensure your part is located, we will design a function that will use a rigorous search, so to speak.

Firstly, we'll allow this function to use :WaitForChild() to account for Client latency. We'll allow a timeout of five seconds—the internal leniency window before a yield-warn—to locate the Instance. If this limit is surpassed while no Instance is found, we'll engage a .ChildAdded signal to listen for new Instances, and to check whether said newly added Instance is the one we were originally looking for.

LocalScript; StarterCharacterScripts.

--###----------[[SERVICES]]----------###--
local Player = game:GetService("Players")



--###----------[[VARAIBLES]]----------###--
local Character = Player.Character or Player.CharacterAdded:Wait()

local ChildAdded;



--###----------[[FUNCTIONS]]----------###--
local function CheckForPart()
    local Part = Character:WaitForChild("Glasses1", 1)
    if (Part) then
        ---------------
        --// Action for when the part is located.
        ---------------
        if (ChildAdded) then
            ChildAdded:Disconnect()
        end
    else
        if (not ChildAdded) then
            ChildAdded = Character.ChildAdded:Connect(CheckForPart)
        end
    end
end



--###----------[[LOGIC]]----------###--
CheckForPart()

You can use a function: ~~~~~~~~~~~~~~~~~ Instance:FindFirstChild("NameHere") ~~~~~~~~~~~~~~~~~

local Players = game:GetService("Players")
Players.Character:FindFirstChild("whatever the name is")