JavaScript method to drag and drop elements in web pages_javascript skills

The example in this article describes the method of dragging elements in a web page using JavaScript. Share it with everyone for your reference. The details are as follows:

This code describes the principles and methods of JS drag and drop in detail, which is worth learning and reference.

/**
* 跨平台的事件监听函数
* @param {Node} node 需要监听事件的DOM节点
* @param {String} eventType 需要监听的事件类型
* @param {Function} callback 事件监听回调函数
* @type Function 返回值为函数类型
* @return 返回监听回调函数的引用，用于释放监听
*/
function bindEvent(node, eventType, callback) {
 if (node.attachEvent) {
  if (eventType.indexOf('on')) { eventType = 'on' + eventType;}
  node.attachEvent(eventType, callback);
 } else {
  if (!eventType.indexOf('on'))
   eventType = eventType.substring(2, eventType.length);
  node.addEventListener(eventType, callback, false);
 }
 return callback;
}
/**
* 跨平台的事件监听卸载函数
* @param {Node} node 需要卸载监听事件的DOM节点
* @param {String} eventType 需要卸载监听的事件类型
* @param {Function} callback 卸载事件监听回调函数
*/
function removeEvent(node, eventType, callback) {
 if (node.detachEvent) {
  if (eventType.indexOf('on')) { eventType = 'on' + eventType;}
  node.detachEvent(eventType, callback);
 } else {
  if (!eventType.indexOf('on'))
   eventType = eventType.substring(2, eventType.length);
  node.removeEventListener(eventType, callback, false);
 }
}
/**
* 兼容不同定位方式的通用拖动接口
* @param {Node} dragger 需要被拖动的元素
*/
//必须告诉系统，哪些元素是可以进行交互，而哪些是不行
function canDrag(dragger) {
 var drag = bindEvent(dragger,'onmousedown',function(e){
  //兼容事件对象
  e = e || event;
  //兼容坐标属性
  var pageX = e.clientX || e.pageX;
  var pageY = e.clientY || e.pageY;
  //兼容样式对象
  var style = dragger.currentStyle || window.getComputedStyle(dragger,null);
  //当没有设置left和top属性时，IE下默认值为auto
  var offX = parseInt(style.left) || 0;
  var offY = parseInt(style.top) || 0;
  //获取鼠标相对于元素的间距
  var offXL = pageX - offX;
  var offYL = pageY - offY;
  //为dragger增加onDrag属性，用来存储拖动事件
  if (!dragger.onDrag) {
   //监听拖动事件
   dragger.onDrag = bindEvent(document,'onmousemove',function(e){
    e = e || event;
    var x = e.clientX || e.pageX;
    var y = e.clientY || e.pageY
    //设置X坐标
    dragger.style.left = x - offXL + 'px';
    //设置Y坐标
    dragger.style.top = y - offYL + 'px';
   });
   //监听拖动结束事件
   dragger.onDragEnd = bindEvent(document,'onmouseup',function(e){
    //释放前读取事件对象
    var x = e.clientX || e.pageX;
    var y = e.clientY || e.pageY
    //释放拖动监听和结束监听
    removeEvent(document, 'onmousemove', dragger.onDrag);
    removeEvent(document, 'onmouseup', dragger.onDragEnd);
    try {
     //删除拖动时所用的属性，兼容FF使用
     delete dragger.onDrag;
     delete dragger.onDragEnd;
    } catch (e) {
     //删除拖动时所用的属性，兼容IE6使用
     dragger.removeAttribute('onDrag');
     dragger.removeAttribute('onDragEnd');
    }
   });
  }
 });
 return function() {
  //返回一个可以取消拖动功能的函数引用
  //释放拖动监听和结束监听
  removeEvent(document, 'onmousemove', dragger.onDrag);
  removeEvent(document, 'onmouseup', dragger.onDragEnd);
  try {
   //删除拖动时所用的属性，兼容FF使用
   delete dragger.onDrag;
   delete dragger.onDragEnd;
  } catch (e) {
   //删除拖动时所用的属性，兼容IE6使用
   dragger.removeAttribute('onDrag');
   dragger.removeAttribute('onDragEnd');
  }
 }
}

I hope this article will be helpful to everyone’s JavaScript programming design.