The comma operator (`,`) evaluates its operands, from left to right, and returns the second one. That's useful in some situations, but just wrong in a `switch` `case`. You may think you're compactly handling multiple values in the case, but only the last one in the comma-list will ever be handled. The rest will fall through to the default.

## Noncompliant Code Example

    switch a {
      case 1,2:  // Noncompliant; only 2 is ever handled by this case
        doTheThing(a);
      case 3:
        doTheOtherThing(a);
      default:
        console.log("Neener, neener!");  // this happens when a==1
    }

## Compliant Solution

    switch a {
      case 1:
      case 2:
        doTheThing(a);
      case 3:
        doTheOtherThing(a);
      default:
        console.log("Neener, neener!");
    }