When I execute a command to create index in mongo shell , it return err as below:
case 1:

db.qrcode.createIndex(\{"accountId":1,"name":1}, \{"backgroud": true})
{
"ok" : 0,
"errmsg" : "WiredTigerIndex::insert: key too large to index, failing  1470 \{ : \"56f37cb8e4b089e98d52ab0e\", : \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa...\" }",
"code" : 17280
}

case 2:

db.tag.createIndex({"tags.value":1,"isDeleted":1,"crowds.text":1}, { background: true }); { "ok" : 0, "errmsg" : "cannot index parallel arrays [crowds] [tags]", "code" : 10088 }

 
But  when I use mongodb driver in my nodejs code to invoke createIndex() method to create the indexes, it both return index name and did't throw any error !
 
I executed getIndexes() command  in mongo shell, In fact the indexes  were not inserted into mongo server.
 
I just found the  above two kinds of error can't be captured, Othens are executed correctly.
 
So I guess the error was not captured in mongodb driver.