console 命令行工具 X clear

console

        var str = "Rome was not built in a day!";
        document.write("y首次出现的下标是：" + str.indexOf("y") + "<br/>");
       document.write('<br/>---------------------------------<br/>');

<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
      
    </script>
</head>
<body>
</body>
</html>