Yep, usually we text "么么哒", it literally means "kiss kiss".

Usually we use the emoji, some girls would say momoda.

yes  we sometimes  use 么么哒 in the  end like  kiss kiss 

Most Chinese people use WeChat to text each other and WeChat comes with its own set of emojis. I myself would use one of those, I'm pretty sure there is a kissing one. Oh yeah, how could I forget?! Chengyu Li is right, most people you write 麼麼噠