I spent a few hours trying to get it to drop me into the espruino REPL right after the code is loaded
Try espruino -p /dev/cu.usbmodem1421 -w yourfile?
espruino -p /dev/cu.usbmodem1421 -w yourfile
@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.
Try
espruino -p /dev/cu.usbmodem1421 -w yourfile
?