[destus]

<div class="simple-collapse">
    <a href="#" class="collapse-control">Control</a>
    <div class="collapse-content" hidden>Content</div>
  </div>
  
  <script>
    
    class SimpleCollapse {
      
      constructor(selector) {
        this.elem = document.querySelector(selector);
      }
      
      init() {
        this.elem.querySelector('a').onclick = this.toggleContent.bind(this);
      }
      
      toggleContent() {
        this.elem.querySelector('.collapse-content').hidden = !this.elem.querySelector('.collapse-content').hidden
      }
      
    }
    
    var obSimpleCollapse = new SimpleCollapse(".simple-collapse"); 
    obSimpleCollapse.init();
    
  </script>