如何在这段代码中加入鼠标悬停停止渐变,移开后继续渐变的功能

 <!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Image slide</title>
    <style type="text/css">
        #img_div {
            height: 375px;
            width: 100%;
            margin: auto;

        }
        #img_div img {
            position: absolute;
            height: 375px;
            width: 100%;
        }
    </style>
    <script type="text/javascript" language="javascript">
        var arr = ["1.jpg", "2.jpg", "3.jpg","4.jpg","5.jpg","6.jpg","7.jpg"];
        window.onload = function () {
            var id = document.getElementById("img_div");
            id.innerHTML = '<img src="' + arr.join('" alt=""><img src="') + '" alt="">';
            id.style.background = "url('" + arr.pop() + "') no-repeat center";
            var img = id.getElementsByTagName("img"), l = arr.length, n = 100;
            (function () {
                var callee = arguments.callee;
                n--;
                if (n < 0) {
                    l--;
                    n = 100;
                    if (l < 0) {
                        l = arr.length;
                        for (var k = img.length; k--;) {
                            img[k].style.opacity = 1;//还原成不透明
                            img[k].style.filter = "alpha(opacity=100)";
                        }
                    }
                    setTimeout(callee, 3000);//每张图片停留3秒(自己调整)
                } else {
                    setTimeout(callee, 30);//30毫秒改变一下透明度(自己调整)
                }
                img[l].style.opacity = n / 100;
                img[l].style.filter = "alpha(opacity=" + n + ")";
            })();
        }
    </script>
</head>
<body>
<div>
    <img src="lunbo2.jpg">
</div>
<div id="img_div">
</div>
<div>
    <img src="lunbo1.jpg">
</div>
</body>
</html>

        var arr = ["1.jpg", "2.jpg", "3.jpg","4.jpg","5.jpg","6.jpg","7.jpg"];
        window.onload = function () {
            var id = document.getElementById("img_div");
            id.innerHTML = '<img src="' + arr.join('" alt=""><img src="') + '" alt="">';
            id.style.background = "url('" + arr.pop() + "') no-repeat center";
            var img = id.getElementsByTagName("img"), l = arr.length, n = 100;
            var timer,isOver///////////
            id.onmouseout = id.onmouseover = function (e) {///////////
                e = e || window.event;
                isOver = e.type == 'mouseover';
                if (isOver) clearTimeout(timer);
                else timer = setTimeout(setOpacity, 3000);
            }
            function setOpacity() {
                n--;
                if (n < 0) {
                    l--;
                    n = 100;
                    if (l < 0) {
                        l = arr.length;
                        for (var k = img.length; k--;) {
                            img[k].style.opacity = 1;//还原成不透明
                            img[k].style.filter = "alpha(opacity=100)";
                        }
                    }
                    if (!isOver) timer = setTimeout(setOpacity, 3000);////////////每张图片停留3秒(自己调整)
                } else {
                    setTimeout(setOpacity, 30);//30毫秒改变一下透明度(自己调整)
                }
                img[l].style.opacity = n / 100;
                img[l].style.filter = "alpha(opacity=" + n + ")";
            }
           setOpacity()
        }