Ask HN: TIL JavaScript switch is weird – why?

[mangeletti]

Given the following, what do you think the console output will be?

    var x = 1;

    switch (x) {
        case 1:
            console.log('case 1');
        case 2:
            console.log('case 2');
        case 3:
            console.log('case 3');
        default:
            console.log('default');
    }

Before you raise your hand, yes I've intentionally omitted the break statements.

And, the answer is:

    case 1
    case 2
    case 3
    default

The switch is designed to execute every case after the first match, which is the reason for placing a `break` after each case.

My assumption was always that the `break` was to avoid wasting the interpreter's time on checking the remaining cases when you knew they'd all be non-matches, not that `break` was basically required.

This means that the switch statement itself is basically useless without `break`, unless each case is ordered in a 1[2,[3,[4]]] fashion (I imagine that's quite rare).

Is this just an artifact taken from C, or is there something else I'm overlooking?

[richardboegli]

Artifact from C. This is by design for consistency. Java does the same.

[davelnewton]

This is how switch statements work in a lot of curly-brace languages.

Intentional fall-through isn't as rare as you seem to think, though--not useless at all.