-edit- Sorry, forget that. The link is for an RN2483.
SX127x doesn't provide any of the LoRaWan logic, so you'd have to do that in JS. I'm afraid it's quite a big project.
@Gordon started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
-edit- Sorry, forget that. The link is for an RN2483.
SX127x doesn't provide any of the LoRaWan logic, so you'd have to do that in JS. I'm afraid it's quite a big project.