拖放问题firefox

当我点击div中的图像并尝试拖动时只拖动图像而不是整个div，当我将其放入新div

    <div class="box" draggable="true">
    <img src="drag icon.png" width="16" height="16"/>
        <header>B</header>
        <p>
        Put me
        </p>
    </div>
    <div class="box" draggable="true">
    <img src="drag icon.png" width="16" height="16"/>
        <header>C</header>
        <p>
        right
        </p>
    </div>
    <div class="box" draggable="true">
    <img src="drag icon.png" width="16" height="16"/>
        <header>D</header>
        <p>
        into
        </p>
    </div>
    <div class="box" draggable="true">
    <img src="drag icon.png" width="16" height="16"/>
        <header>E</header>
        <p>
        the
        </p>
    </div>

脚本:

  (function () {
        var id_ = 'boxes-example';
        var boxes_ = document.querySelectorAll('#' + id_ + ' .box');
        var dragSrcEl_ = null;
        this.handleDragStart = function (e) {
            e.dataTransfer.effectAllowed = 'move';
            e.dataTransfer.setData('text/html', this.innerHTML);
            dragSrcEl_ = this;
            this.style.opacity = '0.5';
            // this/e.target is the source node.
            this.addClassName('moving');
        };
        this.handleDragOver = function (e) {
            if (e.preventDefault) {
                e.preventDefault(); // Allows us to drop.
            }
            e.dataTransfer.dropEffect = 'move';
            return false;
        };
        this.handleDragEnter = function (e) {
            this.addClassName('over');
        };
        this.handleDragLeave = function (e) {
            // this/e.target is previous target element.
            this.removeClassName('over');
        };
        this.handleDrop = function (e) {
            // this/e.target is current target element.
            if (e.stopPropagation) {
                e.stopPropagation(); // stops the browser from redirecting.
            }
            // Don't do anything if we're dropping on the same box we're dragging.
            if (dragSrcEl_ != this) {
                dragSrcEl_.innerHTML = this.innerHTML;
                this.innerHTML = e.dataTransfer.getData('text/html');
            }
            return false;
        };
        this.handleDragEnd = function (e) {
            // this/e.target is the source node.
            this.style.opacity = '1';
            [ ].forEach.call(boxes_, function (box) {
                box.removeClassName('over');
                box.removeClassName('moving');
            });
        };
        [ ].forEach.call(boxes_, function (box) {
            box.setAttribute('draggable', 'true');  // Enable boxes to be draggable.
            box.addEventListener('dragstart', this.handleDragStart, false);
            box.addEventListener('dragenter', this.handleDragEnter, false);
            box.addEventListener('dragover', this.handleDragOver, false);
            box.addEventListener('dragleave', this.handleDragLeave, false);
            box.addEventListener('drop', this.handleDrop, false);
            box.addEventListener('dragend', this.handleDragEnd, false);
        });
    })();

这是一个基本的html5拖放代码示例。你可以选择任意拖放代码来检查这个问题