Sometimes fall-through is useful for grouping cases:
let day = "Saturday"
switch (day) {
case "Saturday":
case "Sunday":
console.log("Weekend")
break
case "Monday":
case "Tuesday":
case "Wednesday":
case "Thursday":
case "Friday":
console.log("Weekday")
break
}
Multiple cases can share the same code block. This is the one legitimate use of fall-through.