script.lua

local Textbox = script.Parent
local service = game:GetService("HttpService")
local jjson = '[{"text":"Hello","bold":"true"},{"text":" World","bold":"true"}]'
local LastJson = ''
local function convert(json)
	local s,r = pcall(function()
		service:JSONDecode(json)
	end)
	if s then
	local DecodedJson = service:JSONDecode(json)
	local XLM = ""
	if DecodedJson[2] then --Many text
		for i,Table in next,DecodedJson do
			local Text = Table["text"]
			local root = Text
			print(root)
			for property,value in next,Table do
				print(property,value)
				if property == "color" then
					root = '<font color="'..value..'">'..root..'</font>'
				end
				if property == "UnderLined" and value == "true" then
						root = '<u>'..root..'</u>'
				end
				if property == "Italic" and value == "true" then
					root = '<i>'..root..'</i>'
				end
                
				if property == "bold" and value == "true" then
					root = '<b>'..root..'</b>'
				end
			end
			XLM = XLM..root
			print(root)
		end
	else
		local Text = DecodedJson["text"]
		XLM = Text
		print("Text = "..Text)
		for property,value in next,DecodedJson do
			if property == "color" then
				print("Color is getting defined")
				XLM = '<font color="'..value..'">'..XLM..'</font>'
			end

			if property == "bold" and value == "true" then
				print("ran")
				XLM = '<b>'..XLM..'</b>'
			end
			end
		end
	
		return XLM
	else
		return false
	end --if s
end



Textbox.FocusLost:Connect(function(bool)
	if bool then
		local r = convert(Textbox.Text)
		if r  then
			LastJson = Textbox.Text
			Textbox.Text = r
		end
	end
end)

Textbox.Focused:Connect(function()
	if LastJson ~= '' then
		Textbox.Text = LastJson
	end
end)

print("Script was created by mrfrinkler")