switch statements

When one value must be compared with several fixed choices, switch is often clearer than a long if-else if chain. JavaScript evaluates the selector once, then jumps to the matching case.

Basic structure

Each case contains a constant followed by a colon. A match runs that branch, break exits the switch, and default handles every unmatched value.

let day = 4;

switch (day) {
    case 1:
        console.log("Monday");
        break;
    case 2:
        console.log("Tuesday");
        break;
    case 3:
        console.log("Wednesday");
        break;
    case 4:
        console.log("Thursday");
        break;
    case 5:
        console.log("Friday");
        break;
    case 6:
    case 7:
        console.log("Weekend");
        break;
    default:
        console.log("Invalid day");
}

This example covers all seven days. Cases 6 and 7 are adjacent and intentionally share one body because they produce the same result.

break and fall-through

Without break, execution continues into the following case; this is called fall-through. Unless several labels intentionally share one body, end each independent branch with break.

Each case contains an expression. JavaScript compares it with the selector using strict equality (===), so the number 1 and the string "1" do not match. Strings and numbers are both common selector values.

Execution order

1. Evaluate the switch selector.
2. Find an equal case; use default if none matches.
3. Execute statements from the matched position.
4. Exit at break or at the end of the switch.

01▶int tier = 2;02 let discount = 0.0;03 switch (tier) {04     case 1:05         discount = 0.05;06         break;07     case 2:08         discount = 0.10;09         break;10     case 3:11         discount = 0.15;12         break;13     default:14         discount = 0.0;15 }16 let payable = 200.0 * (1 - discount);17 console.log(`Payable: ${payable.toFixed(2)}`);