Convert enternt text to "#tags"

I am working on a little projekt and I want to user tags, like below on this form, when asking a question. For an additional example here a picture (the blue node.js i.e.), also multiple tags are needed (like in the example).

Picture of the tag I meant

If someone knows a lib or an example, I would be very happy. Oh, and I am asking, because I was unable to finde anything via Google, maybe I just don't have the right words for the search...

Thanks in advance

Pantastic