Check if youtube video exists.

<!DOCTYPE html>
<html>

  <head>
    <meta charset="utf-8" />
    <title></title>
    <link rel="stylesheet" href="style.css" />
    <script data-require="jquery" data-semver="2.1.3" src="https://code.jquery.com/jquery-2.1.3.min.js"></script>
  </head>

  <body>
    <h5>Youtube id (11 characters):</h5>
    <input type="text" id="youtubeId">
    <div id="info"></div>
    <iframe id="myIframe" width="426" height="240"></iframe>
    <script src="script.js"></script>
  </body>

</html>

var delay = (function() {
  var timer = 0;
  return function(callback, ms) {
    clearTimeout(timer);
    timer = setTimeout(callback, ms);
  };
})();

$('#youtubeId').keyup(function() {
  delay(function() {
    var videoID = $('#youtubeId').val();
    var videos = "https://www.googleapis.com/youtube/v3/videos";
    var apiKey = "AIzaSyAzYHm1iwMocB9pW2uZrz_6Sqte5t_bXGo"; // Insert here your api key
    var fieldsTitle = "fields=items(snippet(title))";
    var fieldsEmpty = "";
    var part = "part=snippet";

    function getUrl(fields) {
      var url = videos + "?" + "key=" + apiKey + "&" + "id=" + videoID + "&" + fields + "&" + part;
      return url;
    }

    $.get(getUrl(fieldsEmpty), function(response) {
      var status = response.pageInfo.totalResults;
      var title;
      if (status) {
        $.get(getUrl(fieldsTitle), function(response) {
          title = response.items[0].snippet.title;
          $('#info').text(title);
          var url = "https://www.youtube.com/embed/" + videoID;
          $('#myIframe').attr('src', url)
        })
      } else {
        title = "Video doesn't exist";
        $('#info').text(title);
        $('#myIframe').attr('src', "");
      }
    });
  }, 1000);
});

#youtubeId {
  display: block;
  width: 426px;
}

#info {
  width: 426px;
  font-weight: bold;
  padding: 20px 0;
}