拖放-代码

var dragDiv = document.getElementById("dragDiv");

            dragDiv.addEventListener("dragover", function (event) {

                event.preventDefault(event);

                console.log("over"); //拖动对象在放置对象上，一直执行

            });

            dragDiv.addEventListener("dragenter", function (event) {

                event.preventDefault(event);

                console.log("enter"); //拖动对象在放置对象上，执行一次

            });

            dragDiv.addEventListener("dragleave", function (event) {

                event.preventDefault(event);

                console.log("leave");//拖动对象离开了放置对象，执行一次

            });