Redner jade block in specific div - node.js

My problem is that I have to render specific block in div #test by ajax. Is it somehow possible?

I also tried to use case statement in jade file ->

block main
  - var friends = 10
  case friends
    when 0
      block test
    default
      block test1

but after any change in JS i could not refresh just "main" block.

Any suggestions?

I have one file with a big amout of blocks and I want to control rendered blocks by changing it in js and ajax refreshing. Other method is the first one i mentioned - rendering specific block in div using ajax.