javascript switch case regex

switch(expression) {
  case x:
    // code block
    break;
  case y:
    // code block
    break;
  default:
    // code block
}

switch(expression) {

  case x:

     // code block

        break;

  case y:

     // code block

     break;

  default:

      // code block

 }
 

var regex1 = /a/,
    regex2 = /b/,
    regex3 = /c/,
    samplestring = 'b';

switch (true) {
    case regex1.test(samplestring):
        console.log("regex1");
        break;
    case regex2.test(samplestring):
        console.log("regex2");
        break;
    case regex3.test(samplestring):
        console.log("regex3");
        break;
}