Adds the specified members to the set stored at key. Specified members that are already a member of this set are ignored. If key does not exist, a new set is created before adding the specified members.
|key||string||key holding the set to add the members to.|
|members||any||members to add to the set.|
|Type||Resolves with||Rejected when|
|Promise<number>||On success, the promise resolves with the number of elements that were added to the set, not including elements already present in the set.|