Is it valid JavaScript to nest an if/else in a switch?

Yes, it is perfectly valid. Have you tried it?

You can combine a switch and an if in a better way, if you really have to:

switch (true) {
    case (foo === 'bar' && raz === 'something'):
        // execute
        break;
    case (foo === 'bar'):
        // do something else
        break;
    default:
        // yada yada
}

_{Sorry to revive such an old post, but it may help people who came here looking how to combine or nest a switch and an if statement.}