String.split with JavaScript-like behaviour in Lua

js-string-split.lua

local function js_string_split(s, f)
    local offset = 1
    local nextOffset = 0
    local result = {}
    if not string.find(s, f) then 
        return { s }
    end
    if f == "" then
        for i = 1, #s do 
            table.insert(result, s:sub(i, i))
        end
        return result
    end
    while true do 
        -- first token
        local pos1, pos2 = string.find(s, f, offset, true)
        if pos1 == nil then 
            break
        end
        -- before first token
        local str_before = s:sub(offset, pos2 - #f)
        table.insert(result, str_before)
        offset = pos2 + 1
        -- is this the last token?
        local nextpos1, nextpos2 = string.find(s, f, offset, true)
        if not nextpos1 then 
            local str_next = s:sub(offset, #s)
            table.insert(result, str_next)
        end
    end
    return result
end