How to handle Shift + Tab inside switch case?

So I have been using a nested if-else & event.which for handling all the keyboard navigation, but I want to change to switch-case & event.key.

I am facing trouble in handling shift+tab event.
I've tried:

switch(event.key){
  case "Shift":
    console.log("entering shift");
    if(event.key === "Tab"){//do something}
    console.log("exiting shift");
    break;
  case "Tab":
    //handling only tab events
    break;
}

But this does not seem to work. The control enters shift block & leaves shift block, without entering if(event.key === "Tab") part. Hence, I'm unable to handle SHIFT + TAB.

Also tried case "Shift" && "Tab":{}, but this is hindering with Tab-only block.

Is there a way to handle SHIFT + TAB inside switch-case.

switch(event.key){
  case "Shift":
    console.log("entering shift");
//you enter this case because event.key === "Shift"
//so event.key === "Tab" will always be false
    if(event.key === "Tab"){//do something}
    console.log("exiting shift");
    break;

I don't think you really need to use switch here as some simple ifs will do fine:

let shift = false;
document.addEventListener('keydown', event => {
  if (event.key === 'Shift') {
     shift = true;
  }
});
document.addEventListener('keyup', event => {
   if (event.key === 'Shift') {
      shift = false;
   }

   if (event.key === 'Tab' && shift) {
      //do stuff
   }
  }
});