Logging temperatur and ground moisture

Is it possible to leave microbit (disconnected from bluetooth and cable) to log temperature with javascript on microbit memory

Yes. In fact this is almost exactly what you want I think - including export to CSV (well, tab-separated): http://www.espruino.com/Data+Collection#simple-example

As others have said the micro:bit is very low on memory - there's 3.6kB of memory for code and data - so the amount of logging you can do is quite small. However you could still do some useful things with it - especially as if you're saving just the time you're probably not going to end up saving more than 20 or so entries.

Hope that helps!