HTML5 拖放元素到屏幕上的任意位置

拖放不会移动元素，如果您希望元素在放置时移动，则必须在放置事件中设置元素的新位置。我做了一个适用于 Firefox 和 Chrome 的示例，以下是要点：

function drag_start(event) {
    var style = window.getComputedStyle(event.target, null);
    event.dataTransfer.setData("text/plain",
    (parseInt(style.getPropertyValue("left"),10) - event.clientX) + ',' + (parseInt(style.getPropertyValue("top"),10) - event.clientY));
} 

该dragstart事件计算出鼠标指针距元素左侧和顶部的偏移量，并将其传递给dataTransfer. 我不担心传递 ID，因为页面上只有一个可拖动元素 - 没有链接或图像 - 如果你的页面上有任何这些东西，那么你将不得不在这里做更多的工作。

function drop(event) {
    var offset = event.dataTransfer.getData("text/plain").split(',');
    var dm = document.getElementById('dragme');
    dm.style.left = (event.clientX + parseInt(offset[0],10)) + 'px';
    dm.style.top = (event.clientY + parseInt(offset[1],10)) + 'px';
    event.preventDefault();
    return false;
}

该drop事件解包偏移量并使用它们相对于鼠标指针定位元素。

该dragover事件只需要preventDefault在任何东西被拖过去时发生。同样，如果页面上还有其他可拖动的内容，您可能需要在此处执行更复杂的操作：

function drag_over(event) {
    event.preventDefault();
    return false;
} 

因此，将其document.body与drop事件一起绑定以捕获所有内容：

var dm = document.getElementById('dragme');
dm.addEventListener('dragstart',drag_start,false);
document.body.addEventListener('dragover',drag_over,false);
document.body.addEventListener('drop',drop,false); 

如果您希望它在 IE 中工作，您需要将 转换aside为a元素，当然，所有事件绑定代码都会有所不同。据我所知，拖放 API 在 Opera 或任何移动浏览器上都不起作用。另外，我知道您说过您不想使用 jQuery，但是跨浏览器事件绑定和操作元素位置是 jQuery 使事情变得更容易的事情。

<aside draggable="true" id="dragme">
    This is an aside, drag me.
</aside>
<p>I never am really satisfied that I understand anything; because, understand it well as I may, my comprehension can only be an infinitesimal fraction of all I want to understand about the many connections and relations which occur to me, how the matter in question was first thought of or arrived at, etc., etc.</p>
<p>In almost every computation a great variety of arrangements for the succession of the processes is possible, and various considerations must influence the selections amongst them for the purposes of a calculating engine. One essential object is to choose that arrangement which shall tend to reduce to a minimum the time necessary for completing the calculation.</p>
<p>Many persons who are not conversant with mathematical studies imagine that because the business of [Babbage’s Analytical Engine] is to give its results in numerical notation, the nature of its processes must consequently be arithmetical and numerical, rather than algebraical and analytical. This is an error. The engine can arrange and combine its numerical quantities exactly as if they were letters or any other general symbols; and in fact it might bring out its results in algebraical notation, were provisions made accordingly.</p>
<p>The Analytical Engine has no pretensions whatever to originate anything. It can do whatever we know how to order it to perform. It can follow analysis, but it has no power of anticipating any analytical revelations or truths. Its province is to assist us in making available what we are already acquainted with.</p>

aside { 
    position:  absolute;
    left: 0;
    top: 0; /* set these so Chrome doesn't return 'auto' from getComputedStyle */
    width: 200px; 
    background: rgba(255,255,255,0.66); 
    border: 2px  solid rgba(0,0,0,0.5); 
    border-radius: 4px; padding: 8px;
}

function drag_start(event) {
    var style = window.getComputedStyle(event.target, null);
    event.dataTransfer.setData("text/plain",
    (parseInt(style.getPropertyValue("left"),10) - event.clientX) + ',' + (parseInt(style.getPropertyValue("top"),10) - event.clientY));
} 
function drag_over(event) { 
    event.preventDefault(); 
    return false; 
} 
function drop(event) { 
    var offset = event.dataTransfer.getData("text/plain").split(',');
    var dm = document.getElementById('dragme');
    dm.style.left = (event.clientX + parseInt(offset[0],10)) + 'px';
    dm.style.top = (event.clientY + parseInt(offset[1],10)) + 'px';
    event.preventDefault();
    return false;
} 
var dm = document.getElementById('dragme'); 
dm.addEventListener('dragstart',drag_start,false); 
document.body.addEventListener('dragover',drag_over,false); 
document.body.addEventListener('drop',drop,false); 

<aside draggable="true" class="dragme" data-item="0">One</aside>
<aside draggable="true" class="dragme second" data-item="1">Two</aside>

function drag_start(event) {
  var style = window.getComputedStyle(event.target, null);
  event.dataTransfer.setData("text/plain", (parseInt(style.getPropertyValue("left"), 10) - event.clientX) + ',' + (parseInt(style.getPropertyValue("top"), 10) - event.clientY) + ',' + event.target.getAttribute('data-item'));
}

function drop(event) {
  var offset = event.dataTransfer.getData("text/plain").split(',');
  var dm = document.getElementsByClassName('dragme');
  dm[parseInt(offset[2])].style.left = (event.clientX + parseInt(offset[0], 10)) + 'px';
  dm[parseInt(offset[2])].style.top = (event.clientY + parseInt(offset[1], 10)) + 'px';
  event.preventDefault();
  return false;
}

var dm = document.getElementsByClassName('dragme');
for (var i = 0; i < dm.length; i++) {
  dm[i].addEventListener('dragstart', drag_start, false);
  document.body.addEventListener('dragover', drag_over, false);
  document.body.addEventListener('drop', drop, false);
}