如何使用HTML和CSS实现拖拽式布局

<div id="container">
  <div class="draggable">元素1</div>
  <div class="draggable">元素2</div>
  <div class="draggable">元素3</div>
  <div class="draggable">元素4</div>
</div>

#container {
  width: 400px;
  height: 300px;
  border: 1px solid #ccc;
  position: relative;
}

.draggable {
  width: 100px;
  height: 100px;
  background-color: #f00;
  position: absolute;
  left: 0;
  top: 0;
  cursor: move;
}

var draggables = document.getElementsByClassName('draggable');
var container = document.getElementById('container');

for (var i = 0; i < draggables.length; i++) {
  draggables[i].addEventListener('dragstart', function (e) {
    e.dataTransfer.setData('text/plain', null);
    e.target.style.opacity = '0.5';
  });

  draggables[i].addEventListener('dragend', function (e) {
    e.target.style.opacity = '1';
  });
}

container.addEventListener('draGover', function (e) {
  e.preventDefault();
});

container.addEventListener('drop', function (e) {
  e.preventDefault();
  var offsetX = e.clientX - container.getBoundinGClientRect().left;
  var offsetY = e.clientY - container.getBoundingClientRect().top;
  var draggable = document.createElement('div');
  draggable.className = 'draggable';
  draggable.style.left = offsetX + 'px';
  draggable.style.top = offsetY + 'px';
  container.appendChild(draggable);
  draggable.addEventListener('dragstart', function (e) {
    e.dataTransfer.setData('text/plain', null);
    e.target.style.opacity = '0.5';
  });

  draggable.addEventListener('dragend', function (e) {
    e.target.style.opacity = '1';
  });
});