Lua, in the browser, mounted per route.

-- pages/counter.lua
local count, setCount = reactive.signal(0)

local root = h("div", {},
    h("p", {}, function()
        return "Count: "..count()
    end),
    h("button", {
        onClick = function() setCount(count()+1) end,
    }, "+")
)

dom.mount(root, "#app")

-- pages/todolist.lua
local items, setItems = reactive.signal({})
local draft, setDraft = reactive.signal("")

reactive.effect(function()
    list.innerHTML = ""
    for _, v in ipairs(items()) do
        dom.append(list, h("li", {}, v))
    end
end)

-- pages/playground.lua (excerpt)
function playground.run()
    local src = __src
    __src = nil
    local chunk, err = load(src, "@playground.lua", "t")
    if not chunk then return err end
    debug.sethook(trip, "", LIMIT)
    local ok, e = pcall(chunk)
    debug.sethook()
    if not ok then return tostring(e) end
end

-- pages/reconcile.lua (excerpt)
elseif l.amount ~= s.amount then
    verdict = "Amount mismatch"
    reason = string.format("Settled %s than the ledger: %s vs %s %s",
        gap(s.amount - l.amount, l.currency), money(s.amount), money(l.amount), l.currency)