Submit on enter except when shift is pressed in JavaScript

Been working on something recently where I wanted to implement a submit handler
when a user hits the enter key in an input. That’s not that big of a deal, sniff
out the key being pressed, and if it’s the Enter key, go ahead and execute the
submit handler.

Since the element in question is an input field, I wanted to allow folks the
ability to hold the shift key to enter new line breaks. Best as I can remember,
this worked fine with textarea elements, but with a Slate.js editor, not so
much.

Not happy with “it is what it is” I decided it was high time that I learned how
to handle the detection of modifier keys in conjunction with other keys being
pressed.

Turns out, it wasn’t all that hard at all. Simply interrogate the shiftKey on
the event to see if the Shift key was being pressed, and continue to check
the key value on the event for the Enter key as per usual.

The end result, in the form of my onKeyPress handler:

const onKeyDown = (event: any): void => {
  if (eventkey === 'Enter' && !event.shiftKey) {
    // Enter was hit by itself, do some stuff!
  }

There’s some other variables you can interrogate as well if sniffing other other
modifier keys in your thing 😉