DataTransfer.clearData()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

DataTransfer.clearData() 方法删除给定类型的拖动操作的 drag data。如果给定类型的数据不存在，则此方法不执行任何操作。

如果调用此方法时没有传入参数，或者参数为空字符串，则将删除所有类型的数据。

此方法不会从拖动操作中删除文件，因此如果有任何文件包含在对象的 DataTransfer.types 列表中，仍然可能有一个类型为“Files”的条目在拖动。

备注： 该方法只能在 dragstart 事件的处理程序中使用，因为这是拖动操作的数据存储唯一能写入的时间。

语法

js
DataTransfer.clearData([format]);

参数

format 可选

一个 string 指定要删除的数据类型。如果此参数为空字符串或未提供，则将删除所有类型的数据。

示例

这个例子显示了使用 DataTransfer 对象的 getData()、setData() 以及 clearData() 方法。

HTML

html
<span class="tweaked" id="source" draggable="true">
  Select this element, drag it to the Drop Zone and then release the selection
  to move the element.
</span>
<span class="tweaked" id="target">Drop Zone</span>
<div>Status: <span id="status">Drag to start</span></div>
<div>Data is: <span id="data">uninitialized</span></div>

CSS

css
span.tweaked {
  display: inline-block;
  margin: 1em 0;
  padding: 1em 2em;
}
#source {
  color: blue;
  border: 1px solid black;
}
#target {
  border: 1px solid black;
}

JavaScript

js
window.addEventListener("DOMContentLoaded", function () {
  // Select HTML elements
  var draggable = document.getElementById("source");
  var dropable = document.getElementById("target");
  var status = document.getElementById("status");
  var data = document.getElementById("data");
  var dropped = false;
  // Register event handlers
  draggable.addEventListener("dragstart", dragStartHandler);
  draggable.addEventListener("dragend", dragEndHandler);
  dropable.addEventListener("dragover", dragOverHandler);
  dropable.addEventListener("dragleave", dragLeaveHandler);
  dropable.addEventListener("drop", dropHandler);
  function dragStartHandler(event) {
    status.textContent = "Drag in process";
    // Change target element's border to signify drag has started
    event.currentTarget.style.border = "1px dashed blue";
    // Start by clearing existing clipboards; this will affect all types since we
    // don't give a specific type.
    event.dataTransfer.clearData();
    // Set the drag's format and data (use event target's id for data)
    event.dataTransfer.setData("text/plain", event.target.id);
    data.textContent = event.dataTransfer.getData("text/plain");
  }
  function dragEndHandler(event) {
    if (!dropped) {
      status.textContent = "Drag canceled";
    }
    data.textContent = event.dataTransfer.getData("text/plain") || "empty";
    // Change border to signify drag is no longer in process
    event.currentTarget.style.border = "1px solid black";
    if (dropped) {
      // Remove all event listeners
      draggable.removeEventListener("dragstart", dragStartHandler);
      draggable.removeEventListener("dragend", dragEndHandler);
      dropable.removeEventListener("dragover", dragOverHandler);
      dropable.removeEventListener("dragleave", dragLeaveHandler);
      dropable.removeEventListener("drop", dropHandler);
    }
  }
  function dragOverHandler(event) {
    status.textContent = "Drop available";
    event.preventDefault();
  }
  function dragLeaveHandler(event) {
    status.textContent = "Drag in process (drop was available)";
    event.preventDefault();
  }
  function dropHandler(event) {
    dropped = true;
    status.textContent = "Drop done";
    event.preventDefault();
    // Get data linked to event format « text »
    var _data = event.dataTransfer.getData("text/plain");
    var element = document.getElementById(_data);
    // Append drag source element to event's target element
    event.target.appendChild(element);
    // Change CSS styles and displayed text
    element.style.cssText =
      "border: 1px solid black;display: block; color: red";
    element.textContent = "I'm in the Drop Zone!";
  }
});

规范

Specification
HTML Standard
# dom-datatransfer-cleardata-dev

浏览器兼容性

BCD tables only load in the browser

参见