DataTransferItemList.length

The read-only length property of the DataTransferItemList interface returns the number of items currently in the drag item list.

Value

The number of drag data items in the list, or 0 if the list is empty or disabled. The drag item list is considered to be disabled if the item list's DataTransfer object is not associated with a drag data store.

Examples

This example shows the use of the length property.

JavaScript

function dragstart_handler(ev) {
  console.log("dragStart");
  // Add this element's id to the drag payload so the drop handler will
  // know which element to add to its tree
  const dataList = ev.dataTransfer.items;
  dataList.add(ev.target.id, "text/plain");
  // Add some other items to the drag payload
  dataList.add("<p>Paragraph…</p>", "text/html");
  dataList.add("http://www.example.org","text/uri-list");
}

function drop_handler(ev) {
  console.log("Drop");
  ev.preventDefault();
  const data = ev.dataTransfer.items;
  // Loop through the dropped items and log their data
  for (let i = 0; i < data.length; i++) {
    if ((data[i].kind === 'string') && (data[i].type.match('^text/plain'))) {
      // This item is the target node
      data[i].getAsString((s) => {
        ev.target.appendChild(document.getElementById(s));
      });
    } else if ((data[i].kind === 'string') && (data[i].type.match('^text/html'))) {
      // Drag data item is HTML
      data[i].getAsString((s) => {
        console.log(`… Drop: HTML = ${s}`);
      });
    } else if ((data[i].kind === 'string') && (data[i].type.match('^text/uri-list'))) {
      // Drag data item is URI
      data[i].getAsString((s) => {
        console.log(`… Drop: URI = ${s}`);
      });
    }
  }
}

function dragover_handler(ev) {
  console.log("dragOver");
  ev.preventDefault();
  // Set the dropEffect to move
  ev.dataTransfer.dropEffect = "move"
}

function dragend_handler(ev) {
  console.log("dragEnd");
  const dataList = ev.dataTransfer.items;
  // Clear any remaining drag data
  dataList.clear();
}

HTML

<div>
  <p
    id="source"
    ondragstart="dragstart_handler(event);"
    ondragend="dragend_handler(event);"
    draggable="true">
    Select this element, drag it to the Drop Zone and then release the selection
    to move the element.
  </p>
</div>
<div
  id="target"
  ondrop="drop_handler(event);"
  ondragover="dragover_handler(event);">
  Drop Zone
</div>

CSS

div {
  margin: 0em;
  padding: 2em;
}

#source {
  color: blue;
  border: 1px solid black;
}

#target {
  border: 1px solid black;
}

Result

Specifications

Specification
HTML Standard
# dom-datatransferitemlist-length-dev

Browser compatibility

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