function minify(jsonString)
    local in_string = false
    local in_multiline_comment = false
    local in_singleline_comment = false
    local string_opener

    local out = {}
    for i=1, #jsonString do
      -- get next (c) and next-next character (cc)

      local c = jsonString:sub(i, i)
      local cc = jsonString:sub(i, i+2)

      -- big switch is by what mode we're in (in_string etc.)
      if in_string then
        if c == string_opener then
          in_string = false
          table.insert(out, c)
        elseif c == '\\' then -- no special treatment needed for \\u, it just works like this too
          table.insert(out, cc)
          i=i+1
        else
          table.insert(out, c)
        end
      elseif in_singleline_comment then
        if c == '\r' or c == '\n' then
          in_singleline_comment = false
        end
      elseif in_multiline_comment then
        if cc == "*/" then
          in_multiline_comment = false
          i=i+1
        end
      else
        -- we're outside of the special modes, so look for mode openers (comment start, string start)
        if cc == "/*" then
          in_multiline_comment = true
          i=i+1
        elseif cc == "//" then
          in_singleline_comment = true
          i=i+1
        elseif c == '"' or c == '\'' then
          in_string = true
          string_opener = c
          table.insert(out, c)
        elseif c ~= ' ' and c ~= '\t' and c ~= '\r' and c ~= '\n' then
          table.insert(out, c)
        end
      end
    end
    return table.concat(out)
  end

Translation of http://jsonminify.tinybrain.de