How to write to gatt characteristic as fast as possible?

A few related things I've found that I shall investigate

• https://github.com/espruino/Espruino/issues/1867 ( https://github.com/espruino/Espruino/commit/766a577e3f5da127ce4815544a31cb7562dfd96c )
  
• https://stackoverflow.com/questions/40328932/javascript-es6-promise-for-loop
  
• https://www.espruino.com/Compilation
  
  

I'm wondering if https://github.com/espruino/Espruino/blob/31c67baa20302b80aafc5b355aade9028a37c471/targets/nrf5x/bluetooth.c#L1593 is lacking error checking that the sd_ble_gattc_write() was successful, as per https://devzone.nordicsemi.com/f/nordic-q-a/49613/sd_ble_gattc_write-and-ble_gattc_evt_write_rsp - what led me there is trying to follow through how Espruino knows the sd_ble_gattc_write() has completed, in case I can find a way to then write the next value quicker than currently. It looks like there's actually just one BLE-related promise at a time https://github.com/espruino/Espruino/blob/31c67baa20302b80aafc5b355aade9028a37c471/libs/bluetooth/jswrap_bluetooth.c#L90 , but I've not yet spotted how we get through to https://github.com/espruino/Espruino/blob/31c67baa20302b80aafc5b355aade9028a37c471/libs/bluetooth/jswrap_bluetooth.c#L96