Flasher.js never gets a mention, but has, for me at least, become a foolproof way to flash ESP8266 with Espruino. I rarely if ever use the esptool.py now. Your mileage may vary but I'd recommend trying it, especially if just starting out.
You can't AFAIK but I've not found it to be an issue. Maybe I've been lucky with the hardware flash chips on my boards. I've got Wemos D1 mini clones and NodeMCU boards all of which are a couple of years old now.
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.
Flasher.js never gets a mention, but has, for me at least, become a foolproof way to flash ESP8266 with Espruino. I rarely if ever use the esptool.py now. Your mileage may vary but I'd recommend trying it, especially if just starting out.