    <!DOCTYPE html>
    <html>
    <head>
      <meta charset="UTF-8">
      <title>input 태그의 값 읽기</title>
      <link rel="stylesheet" href="style_js.css">
    </head>
    <body>
      <form name="myform">
        사용자ID <input type="text" name="userId"><br>
        패스워드 <input type="password" name="passwd"><br>
        <input type="submit" value="log in" onclick="getInput()">
      </form>
      <script>
        function getInput() {
          const id = document.myform.userId;
          const pw = document.myform.passwd;
          if (pw.value.length <= 4)
            alert(`${id.value}님 패스워드를 변경하세요`);
          else
            alert(`${id.value}님 환영합니다`);
        }
      </script>
    </body>
    </html>