Web Component Custom Logic

webcomponent-logic.js

close = root.querySelector('.panel-buttons span.collapse'); //step 1
  
close.addEventListener('click',function(){         //Step 2
    var body = root.querySelector('.panel-body');

    if(body.style.display === 'none'){
      body.style.display = 'block'
    }else{
      body.style.display = 'none';
    }
},false);