Is there a way to get the key state on mouse click?

If the user clicks on the submit button I’d like to check if the shift or ctrl key is down. The last I checked it isn’t available for all events but I thought maybe it would be available on click events.

Test code:

var submitButton = document.createElement("button"); 
// ...
submitButton.addEventListener("click", submitMainForm(event) {
    console.log("Shift:" + event.shiftKey); // always false

Use Case:
Mikael is working on a plugin and screen real estate is limited so he is would like to enable a less used feature to be enabled when the user holds down the ctrl or shift key while clicking on a button.