Multiple logic operators in Javascript

How to determine if a variable matches one of multiple choices in Javascript.

These won't fail, but none will give the results you would likely want:
Case 1:

if (b == 'apple' || 'banana' || 'orange')
   // do something
}

Case 2:

if (b == ('apple' || 'banana' || 'orange'))
   // do something
}

Option 1:
Use the indexOf() method. Note that this method returns 0 or greater if a match is found.
Version A:

if ( ['apple','banana'].indexOf(a) >= 0){
   // do something
}

Version B:

var opt = ['apple','banana'];
if ( opt.indexOf(a) >= 0){
   // do something
}

Option 2:
Use the in operator:
Version A:

if ( a in { 'apple': '', 'banana': '' } ){
   // do something
}

Version B: This may be better if you have many options.

var opt = {
   'apple' : '',
   'banana' : ''
}
if ( a in opt ){
   // do something
}