Video audio continues after closed the popup that contained it

Question

I tried to create a popup with a youtube video inside, but when the popup is closed the video keeps running, I know this because it is still possible to listen to the audio.

javascript, css and html:

// Get the modal
var modal = document.getElementById("myModal");

// Get the button that opens the modal
var btn = document.getElementById("popup_button");

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks on the button, open the modal
btn.onclick = function () {
  modal.style.display = "block";
}

// When the user clicks on <span> (x), close the modal
span.onclick = function () {
  modal.style.display = "none";
}

// When the user clicks anywhere outside of the modal, close it
window.onclick = function (event) {
  if (event.target == modal) {
    modal.style.display = "none";
  }
}

button#popup_button {
    padding: 0px;
    border: none;
    outline: none;
}

 /* The Modal (background) */
 .modal {
    display: none; /* Hidden by default */
    position: fixed; /* Stay in place */
    z-index: 1; /* Sit on top */
    left: 0;
    top: 0;
    width: 100%; /* Full width */
    height: 100%; /* Full height */
    overflow: auto; /* Enable scroll if needed */
    background-color: rgb(0,0,0); /* Fallback color */
    background-color: rgba(0,0,0,0.4); /* Black w/ opacity */
  }
  
  /* Modal Content/Box */
  .modal-content {
    background-color: #fefefe;
    margin: 15% auto; /* 15% from the top and centered */
    padding: 20px;
    border: 1px solid #888;
    width: 50%; /* Could be more or less, depending on screen size */
    height: 50%;
  }

  .modal-content iframe {
    display: block;
    margin: auto;
  }
  
  /* The Close Button */
  .close {
    color: #aaa;
    float: right;
    font-size: 28px;
    font-weight: bold;
  }
  
  .close:hover,
  .close:focus {
    color: black;
    text-decoration: none;
    cursor: pointer;
  }

<img id="popup_button" src="https://img.youtube.com/vi/tgbNymZ7vqY/0.jpg">

<!-- The Modal -->
<div id="myModal" class="modal">

  <!-- Modal content -->
  <div class="modal-content">
    <span class="close">&times;</span>
    <iframe width="97%" height="100%" src="https://www.youtube.com/embed/tgbNymZ7vqY?autoplay=1" allowfullscreen="allowfullscreen"></iframe>
  </div>

</div>

Answer 1

I think if you do a fuction on the close button of the type:

// When the user clicks on <span> (x), close the modal
span.onclick = function () {
  modal.style.display = "none";
  var mVideo = document.getElementById("mVideo");
  mVideo.src = 'https://www.youtube.com/embed/tgbNymZ7vqY?autoplay=0';
}

// When the user clicks anywhere outside of the modal, close it
window.onclick = function (event) {
  if (event.target == modal) {
    modal.style.display = "none";
    var mVideo = document.getElementById("mVideo");
    mVideo.src = 'https://www.youtube.com/embed/tgbNymZ7vqY?autoplay=0';
  }
}

Modal:

<img id="popup_button" src="https://img.youtube.com/vi/tgbNymZ7vqY/0.jpg">

<!-- The Modal -->
<div id="myModal" class="modal">

  <!-- Modal content -->
  <div class="modal-content">
    <span class="close">&times;</span>
    <iframe id="mVideo" width="97%" height="100%" src="https://www.youtube.com/embed/tgbNymZ7vqY?autoplay=1" allowfullscreen="allowfullscreen"></iframe>
  </div>

</div>