This works in regular JavaScript:

function theTest(val) {
  var answer = "";
  switch( val ) {
    case 1: case 2: case 3:
      answer = "Low";
      break;
    case 4: case 5: case 6:
      answer = "Mid";
      break;
    case 7: case 8: case 9:
      answer = "High";
      break;
    default:
      answer = "Massive or Tiny?";
  }
  return answer;
}

theTest(9);

Here's different approach avoiding the switch statement altogether:

var cases = {
  afshin: function() { alert('hey'); },
  _default: function() { alert('default'); }
};
cases.larry = cases.saeed = cases.afshin;

cases[ varName ] ? cases[ varName ]() : cases._default();

In Javascript to assign multiple cases in a switch, we have to define different case without break inbetween like given below:

   <script>
      function checkHere(varName){
        switch (varName)
           {
           case "saeed":
           case "larry":
           case "afshin":
                alert('Hey');
                break;
          case "ss":
               alert('ss');
               break;
         default:
               alert('Default case');
               break;
       }
      }
     </script>

Please see example click on link

I like this for clarity and a DRY syntax.

varName = "larry";

switch (true)
{
    case ["afshin", "saeed", "larry"].includes(varName) :
       alert('Hey');
       break;

    default:
       alert('Default case');

}

If you're using ES6, you can do this:

if (['afshin', 'saeed', 'larry'].includes(varName)) {
   alert('Hey');
} else {
   alert('Default case');
}

Or for earlier versions of JavaScript, you can do this:

if (['afshin', 'saeed', 'larry'].indexOf(varName) !== -1) {
   alert('Hey');
} else {
   alert('Default case');
}

Note that includes won't work in some browser including older IE versions, but you could patch things up fairly easily. See the question determine if string is in list in javascript for more information.

My situation was something akin to:

switch (text) {
  case SOME_CONSTANT || ANOTHER_CONSTANT:
    console.log('Case 1 entered');

  break;

  case THIRD_CONSTANT || FINAL_CONSTANT:
    console.log('Case 2 entered');

  break;

  default:
    console.log('Default entered');
}

The default case always entered. If you're running into a similar multi-case switch statement issue, you're looking for this:

switch (text) {
  case SOME_CONSTANT:
  case ANOTHER_CONSTANT:
    console.log('Case 1 entered');

  break;

  case THIRD_CONSTANT:
  case FINAL_CONSTANT:
    console.log('Case 2 entered');

  break;

  default:
    console.log('Default entered');
}

Adding and clarifying Stefano's answer, you can use expressions to dynamically set the values for the conditions in switch, e.g.:

var i = 3
switch (i) {
    case ((i>=0 && i<=5) ? i : -1):
        console.log('0-5');
        break;

    case 6: console.log('6');
}

So in your problem, you could do something like:

var varName = "afshin"
switch (varName) {
    case (["afshin", "saeed", "larry"].indexOf(varName)+1 && varName):
      console.log("hey");
      break;

    default:
      console.log('Default case');
}

Although it is so much DRY...

In Node.js it appears that you are allowed to do this:

data = "10";
switch(data){
    case "1": case "2": case "3": // Put multiple cases on the same
                                  // line to save vertical space.
        console.log("small");
        break;

    case "10": case "11": case "12":
        console.log("large");
        break;

    default:
        console.log("strange");
        break;
}

This makes for much more compact code in some cases.

Here is one more easy-to-use switch case statement. which can fulfill your requirement. We can use the find method in the switch statement to get the desire output.

    switch(varname){
    case["afshin","saeed","larry"].find(name => name === varname):
        alert("Hey")
        break;
    default:
        alert('Default case');
        break;
}

I use it like this:

switch (true){
     case /Pressure/.test(sensor): 
     {
        console.log('Its pressure!');
        break;
     }

     case /Temperature/.test(sensor): 
     {
        console.log('Its temperature!');
        break;
     }
}

Some interesting methods. For me the best way to solve is using .find.

You can give an indication of what the multiple cases are by using a suitable name inside your find function.

switch (varName)
{
   case ["afshin", "saeed", "larry"].find(firstName => firstName === varName):
       alert('Hey');
       break;

   default:
       alert('Default case');
       break;
}

Other answers are more suitable for the given example but if you have multiple cases to me this is the best way.

It depends. Switch evaluates once and only once. Upon a match, all subsequent case statements until 'break' fire no matter what the case says.

var onlyMen = true;
var onlyWomen = false;
var onlyAdults = false;
 
 (function(){
   switch (true){
     case onlyMen:
       console.log ('onlymen');
     case onlyWomen:
       console.log ('onlyWomen');
     case onlyAdults:
       console.log ('onlyAdults');
       break;
     default:
       console.log('default');
   }
})(); // returns onlymen onlywomen onlyadults

<script src="https://getfirebug.com/firebug-lite-debug.js"></script>

You can use the 'in' operator...
It relies on the object/hash invocation, so it's as fast as JavaScript can be.

// Assuming you have defined functions f(), g(a) and h(a,b)
// somewhere in your code,
// you can define them inside the object, but...
// the code becomes hard to read. I prefer it this way.

o = { f1:f, f2:g, f3:h };

// If you use "STATIC" code can do:
o['f3']( p1, p2 )

// If your code is someway "DYNAMIC", to prevent false invocations
// m brings the function/method to be invoked (f1, f2, f3)
// and you can rely on arguments[] to solve any parameter problems.
if ( m in o ) o[m]()

You can do this:

alert([
  "afshin", 
  "saeed", 
  "larry",
  "sasha",
  "boby",
  "jhon",
  "anna",
  // ...
].includes(varName)? 'Hey' : 'Default case')

or just a single line of code:

alert(["afshin", "saeed", "larry",...].includes(varName)? 'Hey' : 'Default case')

a little improvement from ErikE's answer

I can see there are lots of good answers here, but what happens if we need to check more than 10 cases? Here is my own approach:

 function isAccessible(varName){
     let accessDenied = ['Liam', 'Noah', 'William', 'James', 'Logan', 'Benjamin',
                        'Mason', 'Elijah', 'Oliver', 'Jacob', 'Daniel', 'Lucas'];
      switch (varName) {
         case (accessDenied.includes(varName) ? varName : null):
             return 'Access Denied!';
         default:
           return 'Access Allowed.';
       }
    }

    console.log(isAccessible('Liam'));

The problem with the above approaches, is that you have to repeat the several cases every time you call the function which has the switch. A more robust solution is to have a map or a dictionary.

Here is an example:

// The Map, divided by concepts
var dictionary = {
  timePeriod: {
    'month': [1, 'monthly', 'mensal', 'mês'],
    'twoMonths': [2, 'two months', '2 months', 'bimestral', 'bimestre'],
    'trimester': [3, 'trimesterly', 'quarterly', 'trimestral'],
    'semester': [4, 'semesterly', 'semestral', 'halfyearly'],
    'year': [5, 'yearly', 'annual', 'ano']
  },
  distance: {
    'km': [1, 'kms', 'kilometre', 'kilometers', 'kilometres'],
    'mile': [2, 'mi', 'miles'],
    'nordicMile': [3, 'Nordic mile', 'mil (10 km)', 'Scandinavian mile']
  },
  fuelAmount: {
    'ltr': [1, 'l', 'litre', 'Litre', 'liter', 'Liter'],
    'gal (imp)': [2, 'imp gallon', 'imperial gal', 'gal (UK)'],
    'gal (US)': [3, 'US gallon', 'US gal'],
    'kWh': [4, 'KWH']
  }
};

// This function maps every input to a certain defined value
function mapUnit (concept, value) {
  for (var key in dictionary[concept]) {
    if (key === value ||
      dictionary[concept][key].indexOf(value) !== -1) {
      return key
    }
  }
  throw Error('Uknown "'+value+'" for "'+concept+'"')
}

// You would use it simply like this
mapUnit("fuelAmount", "ltr") // => ltr
mapUnit("fuelAmount", "US gal") // => gal (US)
mapUnit("fuelAmount", 3) // => gal (US)
mapUnit("distance", "kilometre") // => km

// Now you can use the switch statement safely without the need
// to repeat the combinations every time you call the switch
var foo = 'monthly'
switch (mapUnit ('timePeriod', foo)) {
  case 'month':
    console.log('month')
    break
  case 'twoMonths':
    console.log('twoMonths')
    break
  case 'trimester':
    console.log('trimester')
    break
  case 'semester':
    console.log('semester')
    break
  case 'year':
    console.log('year')
    break
  default:
    throw Error('error')
}

One of the possible solutions is:

const names = {
afshin: 'afshin',
saeed: 'saeed',
larry: 'larry'
};

switch (varName) {
   case names[varName]: {
       alert('Hey');
       break;
   }

   default: {
       alert('Default case');
       break;
   }
}

Cleaner way to handle that

if (["triangle", "circle", "rectangle"].indexOf(base.type) > -1)
{
    //Do something
}else if (["areaMap", "irregular", "oval"].indexOf(base.type) > -1)
{
    //Do another thing
}

You can do that for multiple values with the same result

If your case conditions are complex, many case value matches, or dynamic value match required, then it may be best to move that case matching logic to handler child functions.

In your case, if say you had thousands of usernames to match against for a security permissions check for example, this method is cleaner option, more extensible, exposing the high level multi-way branch logic without getting swamped in a long list of case statements.

    switch (varName)
    {     
      case checkPatternAdministrator(varName):
        alert('Hey');
        break;

      case checkPatternUserTypeA(varName):
        alert('Hey2');
        break;

      case checkPatternUserTypeB(varName):
        alert('Hey3');
        break;

      default:
        alert('Default case');
        break;
    }

 function checkPatternAdministrator(varName) {
    // Logic to check Names against list, account permissions etc.
    // return the varName if a match is found, or blank string if not
    var matchedAdministratorName = varName;

    return matchedAdministratorName;
  }

Another way of doing multiple cases in a switch statement, when inside a function:

function name(varName){
  switch (varName) {
     case 'afshin':
     case 'saeed':
     case 'larry':
       return 'Hey';
     default:
       return 'Default case';
   }
}

console.log(name('afshin')); // Hey

Just change the switch condition approach:

switch (true) {
    case (function(){ return true; })():
        alert('true');
        break;
    case (function(){ return false; })():
        alert('false');
        break;
    default:
        alert('default');
}