How to enable elasticsearch auto-complete return only matching word

I need to implement auto-complete but I m not sure about the exact strategy. For example I have the following product :

Highsound Smart Phone Watch for Android (Gray)
So I need when the user starts typing: "s", "sm", "smar" , the word "smart" or "smart watch" to come out rather than the whole phrase: Highsound Smart Phone Watch for Android (Gray)

I looked around how google, amazon etc. do it and they dont display the whole matching record, but rather they display either only the word ("smart") or a phrase ("smart watch").

Right now I enable the automcomplete in elasticsearch according to the following link, but it returns the whole name of the matching record.

https://www.elastic.co/guide/en/elasticsearch/guide/current/_index_time_search_as_you_type.html

Any suggestions?