使用CSS和JavaScript在两个元素之间创建一条线

如果你有一个在另一个之上变得更复杂 – 那么你基本上需要：角度,将它应用于CSS变换：旋转属性,以及两个点/元素之间的长度,以重新计算宽度,因为它不再是直线.我讨厌数学:),所以我使用来自互联网的好人的知识：http://jsfiddle.net/codepo8/bAwUf/light/(信用到codepo8)

两条最重要的路线：

var angle= Math.atan2(red2.offsetTop - red1.offsetTop,red2.offsetLeft - red1.offsetLeft) * 180 / Math.PI;
var length = Math.sqrt((red2.offsetLeft-red1.offsetLeft) * (red2.offsetLeft-red1.offsetLeft) + (red2.offsetTop-red1.offsetTop) * (red2.offsetTop-red1.offsetTop));

现在,您的脚本应该是这样的：

var s = document.querySELEctor(".line");
red1=document.getElementById('RED1');
red2=document.getElementById('RED2');

function allowDrop(ev) {
    ev.preventDefault();
}
function drag(ev) {
    ev.dataTransfer.setData("text",ev.target.id);
}
function drop(ev) {
    ev.preventDefault();
    var data = ev.dataTransfer.getData("text");
    ev.target.appendChild(document.getElementById(data));
 
    s.style.left=red1.offsetLeft+5+'px';
    s.style.top=red1.offsetTop+5+'px';
    
     s.style.visibility='visible';
var angle= Math.atan2(red2.offsetTop - red1.offsetTop,red2.offsetLeft - red1.offsetLeft) * 180 / Math.PI;
var length = Math.sqrt((red2.offsetLeft-red1.offsetLeft) * (red2.offsetLeft-red1.offsetLeft) + (red2.offsetTop-red1.offsetTop) * (red2.offsetTop-red1.offsetTop));
 s.style.width=Math.abs(length)+'px';

     
       s.style.transform="rotate("+Math.round(anglE)+"deg)";
       s.style.transformOrigin ="0 0"; 
     
  
    
}

.div1 {
    width: 150px;
    height: 150px;
    padding: 0px;
    border: 1px solid #aaaaff;
    float: left;
   
}
.line {
  position:absolute;
  height:3px;
  BACkground:red;
  width:100px;
  z-index:999;
  visibility:hidden;
}

<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<div class="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div>

<img id="RED1" src="http://i.imgur.com/By4xvE5.png" draggable="true" ondragstart="drag(event)" align="left">

<img id="RED2" src="http://i.imgur.com/By4xvE5.png" draggable="true" ondragstart="drag(event)" align="left">



<div class="line">

</div>

这是一个很好的起点,我猜(很少有东西可以让它完美),但我想你会得到它……

演示(更好地在这里看到它,片段不是很好,对于这种演示)：https://jsfiddle.net/dxre19o6/