IE上的嵌套事件处理程序

Question

我正在成功添加＆＃34; dragover ＆＃34;，＆＃34; dragleave ＆＃34;和＆＃34; drop ＆＃34;来自＆＃34; dragenter ＆＃34;的事件处理程序触发回调功能。

IE11不会添加树事件处理程序。 有什么建议？

    // Drag-and-drop initiation. 
        if (!isMobile() && window.File && window.FileList && window.FileReader) {
            // Declare global variables.
            var dragStartsInside = false;

            // Initialize scripts.
            addEvent(window, "load", function () {
                for (var e=0; e < elementsArray.length; e++) {
                    // Setup dnd listeners. 
                    addEvent(elementsArray[e], "dragstart", function() {dragStartsInside = true; } ); 
                    addEvent(elementsArray[e], "dragenter", dragEnter); 
                    addEvent(elementsArray[e], "dragend", function() {dragStartsInside = false; } ); 
                }
            }); 

            // Drag and drop events. 
            function dragEnter(evt) { 
                cancelBubble(evt); 
                if (!dragStartsInside) {
                    // Add "dragStartsInside"-dependent events. 
                    addEvent(evt.target, "dragover", dragOver); 
                    addEvent(evt.target, "dragleave", dragLeave); 
                    addEvent(evt.target, "drop", drop); 
                }
                return cancelDefaultAction(evt);
            }

            function dragOver(evt) {
                cancelBubble(evt);
                ...
                return cancelDefaultAction(evt);
            }

            function drop(evt) {
                cancelBubble(evt);
                dragLeave(evt); 
                ...
                return cancelDefaultAction(evt);
            }

            function dragLeave(evt) {
                removeEvent(evt.target, "dragover", dragOver); 
                removeEvent(evt.target, "dragleave", dragLeave); 
                removeEvent(evt.target, "drop", drop); 
            }
        }