Comment by TAForObvReasons

You can switch on arbitrary types in JS and you can add expressions:

    switch(3) { 
      case true: break;
      case "ab" + "c": break;
      case Math.random() >= 0.5 ? "heads" : new Error("tails") : break;
    }

The optimizer will have to be persuaded that the switch and each case is integral before optimizing with a jump table. On the other hand, Arrays typically have a fast path for integer indices.