Detect if Class has an element inside of certain Class?

I’m trying to get an Alert if a class contains an element of a certain class.

My attempt: https://jsfiddle.net/d9qecgjx/1/

HTML

<div class="parent">

  <div class = "child1">
  </div>
  
  <div class = "child2">
  </div>
  
  <div class = "child3">
  </div>
  
  <div class = "child4">
  </div>

</div>

jQuery

if ( $( ".parent" ).hasClass( ".child3" ) ){
                alert("You have that");
}

if ( $( ".parent" ).find( ".child3" ).length ){
                alert("You have that");
}