How to apply a class only to the first child of an element in less?

Question

css

On the less screen, property width:200px; applies to all divs in the "parent" class. Tell me how to apply the class in less not to all divs, but only to the first child "child_1"?

Answer 1

.parent {
  >div {width: 200px;}
}

Answer 2

www.prntscr.com/h4azjm

Answer 3

didn't use classList.add to add before, so I can't say, setAttribute class/className instead (latest for old IE)

Answer 4

How is it not if there is. Function not found says... In the script settings, select no Wrap in head.