Adds a new thing to the set and returns the number of things which are
actually added to the set. For example my_set.add(#42);
will return 0
if my_set
already contains thing #42
.
This function generates a change (except when called on a variable).
set.add(thing1, thing1, ..., thingX)
Returns the number of things
which are added to the set.
This code adds things to a set:
s = set();
a = {item: 'a'};
b = {item: 'b'};
// add both `a` and `b` to set `s`; note that `a` is only added once;
s.add(a, a, b);
Return value in JSON format
2