console 命令行工具 X clear
console
<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8" />
        <title></title>
    </head>
    <body>
        <script>
            function Reverse(str)
            {
            var arr =[];
            for(var i=str.length-1;i>=0;i--)
                {
                arr.push(str[i]);
                }
            return arr.join("");
            }
        document.write(Reverse('abcde')); 
        document.write("<br />");
        </script>
    </body>
</html>