BasicSytax

Switch can "fall through" without break --[MDN](A re-introduction to JavaScript (JS tutorial) - JavaScript | MDN (mozilla.org))

situation 1

function eatIt(){ console.log("eat")};
var a = 1

switch (a) {
  case 1: // fallthrough
  case 2:
    eatIt();
    break;
  default:
    doNothing();
}

output will be

eat

situation 2

switch (a) {
  case 1:     
    eatIt();
// fallthrough
  case 2:
    eatIt();
    break;
  default:
    doNothing();
}

output will be

eat
eat