Thanks @guycreate, I received my two TTGO boards and it was really easy to install Espruino on it.
I started to play with it and it sounds really promising :)
Do you know if it is possible to use the built in RST and PRG buttons with Espruino ?
Here is the pin diagram of my board: https://ae01.alicdn.com/kf/HTB1V_aBbTnI8KJjSszbq6z4KFXaH.jpg
I don't know which pins correspond to these buttons :(