We can perform the following operations on sets:
Union: Given two sets, this returns a new set with the elements from both given sets
Intersection: Given two sets, this returns a new set with the elements that exist in both sets
Difference: Given two sets, this returns a new set with all elements that exist in the first set and do not exist in the second set
Subset: This confirms whether a given set is a subset of another set
The mathematic concept of union is that the union of sets A and B, denoted by 
, is the set defined as:
This means that x (the element) exists in A or x exists in B. The following diagram exemplifies the union operation:
Now let's implement the union method in our Set class:
this.union = function(otherSet){
var unionSet = new Set(); //{1}
var values = this.values(); //{2}
for (var i=0; i<values.length; i++){
unionSet.add(values[i]);
}
values = otherSet.values(); //{3}
for (var i=0; i<values.length; i++){
...