tokens: You might need to implement a performance test to be sure about the actual difference , but I guess it should be a minimal impact , because binding events on the document will mean that you catch any element event once it bubbles to the top-most element in the document .
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O