HTML
<!DOCTYPE html>
<html lang="ko">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Hello jQuery</title>
  <link rel="stylesheet" href="../css/all.min.css">
  <link rel="stylesheet" href="../css/bootstrap.min.css">
  <link rel="stylesheet" href="../css/base.css">
  <script src="../js/jquery.min.js"></script>
</head>
<body>
  <img src="../img/house2.jpg" id="img" onclick="hideImg()";>

  <script src="../js/util.js"></script>
  <script src="../js/01.hello.js"></script>
</body>
</html>

01.hello.js
console.log($)
console.log(jQuery)

function hideImg() {
  var img = document.getElementById('img');
  var opacity = 1;
  var interval = setInterval(function () {
    opacity -= 0.01;
    img.style.display = opacity
    if(opacity < 0) {
      img.style.display ='none';
      clearInterval(interval);
    }
  }, 10);
}

선생님이 쓴거 그대로 베껴 쓴건데 왜 난 안되는거지
여러번 클릭하니 페이드아웃효과없이 그냥 휙 사라짐
살려줘