为什么focus（）不能用于div元素？

Question

  var targetElement = document.getElementsByClassName('hello-world-div')[0];
  var focusElement = document.activeElement;
  console.log("currently focused on: ");
  console.log(focusElement); //this shows the body element  

  targetElement.focus();
  focusElement = document.activeElement;
  console.log("forced focus on: ");
  console.log(focusElement); // this still shows the body element

为什么焦点元素不会改变？

Answer 1

我必须将tabIndex属性添加到“hello-world-div”元素，以便focus（）和blur（）可以工作！