regarding bootloader - Bangle has different display and buttons so the bootloader itself won't run well on PineTime as is but yes, one can build espruino and its bootloader for pinetime pretty easily. the nearest to PineTime is P8 watch and there are several projects using espruino on P8. So for pinetime it just needs changing some pin numbers, otherwise the hardware is basically same as P8.
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.
regarding bootloader - Bangle has different display and buttons so the bootloader itself won't run well on PineTime as is but yes, one can build espruino and its bootloader for pinetime pretty easily. the nearest to PineTime is P8 watch and there are several projects using espruino on P8. So for pinetime it just needs changing some pin numbers, otherwise the hardware is basically same as P8.
see https://github.com/jeffmer/P8Apps or https://github.com/enaon/eucWatch however due to different pinout it won't run as is.
However if you have SWD working you can try to flash my build for P8 https://github.com/fanoush/ds-d6/blob/master/espruino/DFU/P8/espruino_2v08.189_p8_SDK12_SD30.hex and it should hopefully run (except button - BTN1 - P8 has it on pin 17)