مفتاح

switch picks a case

• switch compares one value against several possible matches, called cases.
• It is a tidy alternative to a long if … else if chain that tests the same variable.
• default runs when no case matches, like a final else.

let day = "sat";
switch (day) {
  case "sat":
    console.log("Weekend");
    break;
  case "mon":
    console.log("Back to school");
    break;
  default:
    console.log("A school day");
}
// → Weekend

break ends the case

• break jumps out of the switch.
• Without it, JavaScript keeps going into the next case. This is called fall-through.
• Fall-through is useful on purpose: stack several cases that share one action.

let day = "sun";
switch (day) {
  case "sat":
  case "sun":
    console.log("Weekend");
    break;
  default:
    console.log("Weekday");
}
// → Weekend

Worked example: points for a medal

Question: a medal is "gold", "silver" or "bronze". Gold scores 3 points, silver 2, bronze 1, and anything else 0.

let medal = "silver";
let points;
switch (medal) {
  case "gold":
    points = 3;
    break;
  case "silver":
    points = 2;
    break;
  case "bronze":
    points = 1;
    break;
  default:
    points = 0;
}
console.log(points);
// → 2

The switch only chooses. The single console.log after it prints the result, whichever case ran.

Watch out

• switch compares with ===. So case 1 does not match the string "1".
• A case tests one exact value. For ranges such as "70 or more", use if … else if.

Common mistakes

• Forgetting break. The next case runs too, and its value overwrites yours.
• Writing case "gold" || "silver":. That is one value, "gold". Stack two case lines instead.
• Putting default above another case without a break. It still runs only when nothing matches, but then it falls through into the case below. Keep default last.

Now you try

• Choose a value with switch, then share one action between two cases.
• Press Check answer to test it.