4.9 手动翻页的循环广告

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="refresh" content="20">
    <link rel="stylesheet" href="myCSS.css">
    <script>
        var index = 0;
        function forward() {
            var images = ["src/test_on.png","src/test_off.png"];
            var myImage = document.getElementById("myImageID");
            myImage.src = images[Math.abs(index % 2)];
            index++;
        }
        function backward() {
            var images = ["src/test_on.png","src/test_off.png"];
            var myImage = document.getElementById("myImageID");
            myImage.src = images[Math.abs(index % 2)];
            index--;
        }
        function linkChange() {
            document.getElementById("myImageID").parentNode.onclick = function () {
                var links = ["https://www.baidu.com","https:www.google.com"];
                document.location.href = links[index%2];
                return false;
            };
        }
        window.onload = linkChange;
    </script>
</head>
<body>
<a href="https://www.baidu.com"><img id="myImageID" src="src/test_on.png"></a>
<button onclick="forward()">下一个</button>
<button onclick="backward()">上一个</button>
</body>
</html>