console 命令行工具 X clear
console
<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
        var x = 4;
        var y = 8;
        if (x < 5)
        {
            if (y < 5)
            {
                document.write("x小于5，y小于5");
            }
            else
            {
                document.write("x小于5，y大于5");
            }
        }
        else
        {
            if (y < 5)
            {
                document.write("x大于5，y小于5");
            }
            else
            {
                document.write("x大于5，y大于5");
            }
        }
    </script>
</head>
<body>
</body>
</html>