Pete Nicholls Pete Nicholls - 3 months ago 8
HTML Question

prevent drop inside a child element when drag & dropping with JS

I've created a simple drag and drop setup, 2 divs that allow a user to drag a child div between the two. It works fine unless a 'child div' is dropped directly inside another. I've been trying to wrap my head around it for hours and there must be a simple solution i am missing.

You can see a (not quite) working demo here
https://preview.c9.io/teemoash/fantasyleague/gamething/pete.html?_c9_id=livepreview4&_c9_host=https%3A%2F%2Fide.c9.io

any help is greatly appreciated

Thanks!

The html is very simple. ( note that i have tried returning false on onDrop and onDragOver events)

<div id = "squad" ondrop="drop(event)" ondragover="allowDrop(event)">
<h1>SQUAD</h1>
<div id = "jeff" class = "champion" draggable = "true" ondragstart="drag(event)" ondrop = "return false" ondragover="return false">
<h1>Jeff</h1>

<div class = "attributes">
<div class = "number kills"><span> 4</span><p>Kills</p></div>
<div class = "number deaths"><span>2 </span><p>Deaths</p></div>
<div class = "number GPM"><span> 12</span><p>GPM</p></div>

</div>
</div>


<div id = "Geoff" class = "champion" draggable = "true" ondragstart="drag(event)" ondrop = "return false" ondragover="return false">
<h1>Geoff</h1>

<div class = "attributes">
<div class = "number kills"><span> 7</span><p>Kills</p></div>
<div class = "number deaths"><span>0 </span><p>Deaths</p></div>
<div class = "number GPM"><span> 14</span><p>GPM</p></div>

</div>
</div>

<div id = "jeph" class = "champion" draggable = "true" ondragstart="drag(event)" ondrop = "return false" ondragover="return false">
<h1>Jeph</h1>

<div class = "attributes">
<div class = "number kills"><span> 1</span><p>Kills</p></div>
<div class = "number deaths"><span>9 </span><p>Deaths</p></div>
<div class = "number GPM"><span> 24</span><p>GPM</p></div>

</div>
</div>

</div> <!-- end of squad div-->

<div id = "myTeam" ondrop="drop(event)" ondragover="allowDrop(event)">
<h1>My Team</h1>

</div>

<div id = "scores">
<h1>My Team Scores</h1>
</div>


and the js looks like this;

<script>


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));

}
</script>

Answer

The problem is that the drop is tied to the event, but the way you have it it should just be tied to the element like this:

function drop(ev, el) {
  ev.preventDefault();
  var data = ev.dataTransfer.getData("text");
  el.appendChild(document.getElementById(data));
}

Then change your drop(event) to drop(event, this) in your two ondrop events. Take a look at the snippet in Full Page mode to see that it works.

function allowDrop(ev) {
  ev.preventDefault();
}

function drag(ev) {
  ev.dataTransfer.setData("text", ev.target.id);
}

function drop(ev, el) {
  ev.preventDefault();
  var data = ev.dataTransfer.getData("text");
  el.appendChild(document.getElementById(data));
}
* {
  margin: 0;
  box-sizing: border-box;
}
#squad {
  width: 40vw;
  height: 90vh;
  overflow-y: scroll;
  border-radius: 10px;
  margin-left: 5vw;
  margin-top: 5vh;
  background-color: red;
  float: left;
}
h1 {
  text-align: center;
}
#myTeam {
  float: left;
  height: 60vh;
  width: 40vw;
  border-radius: 10px;
  background-color: red;
  margin-left: 10vw;
  margin-top: 5vh;
}
#scores {
  width: 40vw;
  height: 25vh;
  margin-top: 5vh;
  margin-left: 10vw;
  background-color: red;
  border-radius: 10px;
  float: left;
}
.champion {
  width: 90%;
  height: 15vh;
  margin: 1%;
  padding: 2%;
  border: 1px black solid;
  background-color: white;
  border-radius: 10px;
  overflow: hidden;
}
.champion h1 {
  float: left;
}
.attributes {
  margin-left: 10%;
  float: left;
}
.number {
  float: left;
  text-align: center;
  margin-left: 10px;
}
#div1,
#div2 {
  width: 90%;
  height: 15vh;
  margin: 1%;
  border: 1px black solid;
  border-radius: 10px;
}
<div id="squad" ondrop="drop(event, this)" ondragover="allowDrop(event)">
  <h1>SQUAD</h1>

  <div id="jeff" class="champion" draggable="true" ondragstart="drag(event)" ondrop="return false" ondragover="return false">
    <h1>Jeff</h1>

    <div class="attributes">
      <div class="number kills"><span> 4</span>
        <p>Kills</p>
      </div>
      <div class="number deaths"><span>2 </span>
        <p>Deaths</p>
      </div>
      <div class="number GPM"><span> 12</span>
        <p>GPM</p>
      </div>
    </div>
  </div>
  <div id="Geoff" class="champion" draggable="true" ondragstart="drag(event)" ondrop="return false" ondragover="return false">
    <h1>Geoff</h1>

    <div class="attributes">
      <div class="number kills"><span> 7</span>
        <p>Kills</p>
      </div>
      <div class="number deaths"><span>0 </span>
        <p>Deaths</p>
      </div>
      <div class="number GPM"><span> 14</span>
        <p>GPM</p>
      </div>
    </div>
  </div>
  <div id="jeph" class="champion" draggable="true" ondragstart="drag(event)" ondrop="return false" ondragover="return false">
    <h1>Jeph</h1>

    <div class="attributes">
      <div class="number kills"><span> 1</span>
        <p>Kills</p>
      </div>
      <div class="number deaths"><span>9 </span>
        <p>Deaths</p>
      </div>
      <div class="number GPM"><span> 24</span>
        <p>GPM</p>
      </div>
    </div>
  </div>
</div>
<!-- end of squad div-->
<div id="myTeam" ondrop="drop(event, this)" ondragover="allowDrop(event)">
  <h1>My Team</h1>

</div>
<div id="scores">
  <h1>My Team Scores</h1>

</div>