var set = new Set([1,2,3]);
The .has method will check if the value is contained within the set.
var hasTwo = set.has(2);
The .size method will return an integer representing the size of the Set
var howBig = set.size;
checkSet([4, 5, 6], 3)
should return [ false, 3 ]
testString: 'assert((function(){var test = checkSet([4,5,6], 3); return DeepEqual(test, [ false, 3 ]);})(), "checkSet([4, 5, 6], 3)
should return [ false, 3 ]");'
```