JavaScript implements the drag-and-drop function of multiple elements

Question

I found this code that allows you to drag and drop an item within a specific area, but I can't rewrite it to allow multiple elements to be dragged and dropped because I don't know how to get the drag from the drop_handler function The id of the object.

let offsetX;
let offsetY;

onDragStart = function(ev) {
  const rect = ev.target.getBoundingClientRect();

  offsetX = ev.clientX - rect.x;
  offsetY = ev.clientY - rect.y;
};

drop_handler = function(ev) {
  ev.preventDefault();

  const left = parseInt(id2.style.left);
  const top = parseInt(id2.style.top);

  id1.style.position = 'absolute';
  id1.style.left = ev.clientX - left - offsetX + 'px';
  id1.style.top = ev.clientY - top - offsetY + 'px';
  id2.appendChild(document.getElementById("id1"));
};

dragover_handler = function(ev) {
  ev.preventDefault();
  ev.dataTransfer.dropEffect = "move";
};

<div id="id1" draggable="true" ondragstart="onDragStart(event)" style="border:2px solid green; cursor:pointer;width:100px;height:50px;">拖动的Div</div>


<div id="id2" style="position:absolute;left:200px;top:50px;border:2px solid red; cursor:pointer;width:200px;height:200px;" ondrop="drop_handler(event)" ondragover="dragover_handler(event)">放置的Div
</div>

Answer 1

In onDragStart, "save" dragElement. This way you can use this variable in drop_handler to move items.

I added a const to dropElement because it won't change.

let offsetX;
let offsetY;
let dragElement = null;
const dropElement = document.getElementById("id-drop");

onDragStart = function(ev) {
  const rect = ev.target.getBoundingClientRect();

  offsetX = ev.clientX - rect.x;
  offsetY = ev.clientY - rect.y;
  
  dragElement = ev.target;
};

drop_handler = function(ev) {
  ev.preventDefault();

  const left = parseInt(dropElement.style.left);
  const top = parseInt(dropElement.style.top);

  dragElement.style.position = 'absolute';
  dragElement.style.left = ev.clientX - left - offsetX + 'px';
  dragElement.style.top = ev.clientY - top - offsetY + 'px';
  dropElement.appendChild(dragElement);
};

dragover_handler = function(ev) {
  ev.preventDefault();
  ev.dataTransfer.dropEffect = "move";
};

<div id="id1" draggable="true" ondragstart="onDragStart(event)" style="border:2px solid green; cursor:pointer;width:100px;height:50px;">拖动的Div #1</div>

<div id="id2" draggable="true" ondragstart="onDragStart(event)" style="border:2px solid green; cursor:pointer;width:100px;height:50px;">拖动的Div #2</div>

<div id="id-drop" style="position:absolute;left:200px;top:50px;border:2px solid red; cursor:pointer;width:200px;height:200px;" ondrop="drop_handler(event)" ondragover="dragover_handler(event)">放置的Div
</div>