HTML5原生拖放实例分析

*{
    margin: 0;
    padding: 0;
}
body{
    -webkit-user-select: none; 
       -moz-user-select: none; 
       -ms-user-select: none; 
       user-select: none;
}
#wrap{
    height: 100px;
    text-align: center;
}
img{
    width: 100px;
    height: 100px;
    cursor: -webkit-grab;
    cursor: -moz-grab;
    cursor: grab;
}
#cart{
    width: 500px;
    height: 100px;
    border-radius: 20px;
    margin: 50px auto 0;
    background-color: orange;
}
#cart.hover{
    background-color: red;
}
#cart img{
    width: 70px;
    height: 70px;
    margin: 15px;
}

//被拖动元素的三个事件
function dragstart(e){
  e = EventUtil.getEvent(e);
  var target = EventUtil.getTarget(e);
  e.dataTransfer.setData("text",target.title);
  //因为IE10、IE11和Edge不支持setDragImage()方法，需要判断
  if(e.dataTransfer.setDragImage){
    e.dataTransfer.setDragImage(target,50,50); 
  }
  
  //effectAllowed事件和dropEffect事件搭配使用
  e.dataTransfer.effectAllowed = 'move';
  dragElement = target;
}
function drag(e){
  e = EventUtil.getEvent(e);
  var target = EventUtil.getTarget(e);
  setOpacity(target,0);
}
function dragend(e){
  e = EventUtil.getEvent(e);
  var target = EventUtil.getTarget(e);
  setOpacity(target,1);
}

//放置目标的四个事件
function dragenter(e){
  e = EventUtil.getEvent(e);
  var target = EventUtil.getTarget(e);
  //重要！重写dragenter事件的默认行为，使其可以触发drop事件
  EventUtil.preventDefault(e); 
  //dropEffect事件和effectAllowed事件搭配使用
  e.dataTransfer.dropEffect = 'move';
  target.className = 'hover';
}
function dragover(e){
  e = EventUtil.getEvent(e);
  //重要！重写dragover事件的默认行为，使其可以触发drop事件
  EventUtil.preventDefault(e); 
}
function dragleave(e){
  e = EventUtil.getEvent(e);
  var target = EventUtil.getTarget(e);
  target.className = '';
}
function drop(e){
  e = EventUtil.getEvent(e);
  var target = EventUtil.getTarget(e);
  var title = e.dataTransfer.getData("text");
  console.warn('把%s添加到购物车中！',title);
  target.className = '';
  dragElement.parentNode.removeChild(dragElement);
  var img = dragElement.cloneNode();
  img.draggable = false;
  setOpacity(img,1);
  cart.appendChild(img);

  //重要！为了让Firefox支持正常的拖放，取消drop事件的默认行为
  EventUtil.preventDefault(e); 
}


//设置透明度
function setOpacity(element,value){
  if(typeof element.style.opacity!='undefined'){
    element.style.opacity=value;
  }else{
    element.style.filter = "alpha(opacity="+value*100+")";        
  }
}
//事件处理，做兼容处理
var EventUtil={    
  //添加事件处理程序
  addHandler:function(element,type,handler){     
    if(element.addEventListener){          
      element.addEventListener(type,handler,false);    
    }else if(element.attachEvent){           
      element.attachEvent("on"+type,handler);      
    }else{         
      element["on"+type]=handler;           
    }   
  },      
  //获取事件对象
  getEvent:function(event){       
    return event?event:window.event;   
  },     
  //获取事件的目标
  getTarget:function(event){      
    return event.target||event.srcElement;   
  },    
  //取消默认事件
  preventDefault:function(event){       
    if(event.preventDefault){         
      event.preventDefault();       
    }else{         
      event.returnValue=false;      
    }   
  }
};

var imgs = document.getElementsByTagName("img"),
    cart = document.getElementById('cart'),
    dragElement = null;

for(var i=0; i ){
  EventUtil.addHandler(imgs[i],'dragstart',dragstart);
  EventUtil.addHandler(imgs[i],'drag',drag);
  EventUtil.addHandler(imgs[i],'dragend',dragend);
}
EventUtil.addHandler(cart,'dragenter',dragenter);
EventUtil.addHandler(cart,'dragover',dragover);
EventUtil.addHandler(cart,'dragleave',dragleave);
EventUtil.addHandler(cart,'drop',drop);