$('#clickme').click(function() {
  $('#book').toggle('slow', function() {
    // Animation complete.
    alert($('#book').is(":visible")); //<--- TRUE if Visible False if Hidden
  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="clickme">
  Click here
</div>
<img id="book" src="https://upload.wikimedia.org/wikipedia/commons/8/87/Google_Chrome_icon_%282011%29.png" alt="" width="300"/>

function toggle() {
  $(content).toggle();
  let visible= content.style.display != 'none'
  console.log('visible:', visible);
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<button onclick="toggle()">Show/hide</button>
<div id="content">ABC</div>