how to toggle div in jquery with unicode arrow only

$('.hide-show').hide();
$('.toggle-year').on('click', function() {
  $(this).html($(this).text().substr(0, 4) == 'Hide' ? '▼' : 'Hide ▲');
  $('.hide-show').toggle('slow');
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<a href="javascript:void(0)" class="toggle-year">&#9660;</a>
<div class="hide-show">
  Content comes here
</div>

// hides the text to be hidden on page-load:
$('.hide-show').hide();

// selects all elements matching the supplied CSS selector
// and binds the anonymous function of the on() method
// as the event-handler for the 'click' event:
$('.toggle-year').on('click', function() {
  $(this).text(function(_, currentText) {

  // _ is the index of the current element amongst
  // all the elements retrieved in the jQuery collection;
  // currentText is a reference to the current textContent
  // of the current element from the jQuery collection.


  // here we use a conditional operator to update the
  // text of the current element. If the currentText is
  // equal to '▼' then we change it to '▲' and if it
  // is not equal to '▼' then we set it to '▼':
    return currentText == "▼" ? "▲" : "▼";
  });

  // and then we toggle the visibility of the hidden
  // element(s):
  $('.hide-show').toggle('slow');
});

/* we're using a <button> instead of an <a> as we're not
   navigating to a new area of the website, so here we're
   styling it to appear similar to an <a> (assuming that's
   your preference): */
button.toggle-year {
  border: 0;
  background-color: inherit;
  text-decoration: underline;
  color: #00f;
  outline: 0;
}

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

<!-- as mentioned in the CSS, above, because we're not using
     the element for navigation but instead for functionality,
     I've replaced the <a> with a <button>: -->
<button class="toggle-year">&#9660;</button>
<div class="hide-show">
  Content comes here
</div>

// I cache a reference to the document as 'D' because I'm lazy and don't want
// to type 'document' more than I have to:
const D = document,
  // here we define the toggleVisibility function, using Arrow function syntax
  // since we don't really need a reference to 'this', and we get an indirect
  // access via the Event Object passed from EventTarget.addEventListener()
  // function later:
  toggleVisibility = (e) => {
  
    // e.target is the element that initiated the click action (in this
    // instance e.currentTarget would also have worked):
    const clicked = e.target,
    
      // caching a reference to the current textContent of that clicked
      // element:
      text = clicked.textContent,
      
      // caching a reference to the element(s) that we intend to show/hide:
      elementsToHide = D.querySelectorAll('.hide-show'),
      
      // we're using this test in two places, so cache the result of the
      // comparison/assessment:
      shouldChange = text == '▼';

    // iterating over the collection of elements we found earlier, using
    // NodeList.protoype.forEach():
    elementsToHide.forEach(
      // again using an Arrow function syntax:
      (el) => {
      
        // if the shouldChange variable is true/truthy (in this case it's
        // Boolean true, but it would also work with truthy/falsey values)
        // we change the display of the current Node in the NodeList to
        // 'block', otherwise if shouldChange is false then we set the
        // display to 'none' in order to hide it:
        el.style.display = shouldChange ? 'block' : 'none';
        
        // here if shouldChange is true we update the text-content to
        // '▲', otherwise we change it to '▼':
        clicked.textContent = shouldChange ? '▲' : '▼';
      });
  },
  
  // here we retrieve the <button> elements with the class-name of 'toggle-year':
  toggleButtons = D.querySelectorAll('button.toggle-year');

// and then use NodeList.prototype.forEach() to iterate over that collection:
toggleButtons.forEach(
  // again, we use Arrow syntax and bind the toggleVisibility() function (but
  // do note the deliberate lack of parentheses below) as the event-handler for
  // the 'click' event:
  (button) => button.addEventListener('click', toggleVisibility)
);

button.toggle-year {
  border: 0;
  background-color: inherit;
  text-decoration: underline;
  color: #00f;
  outline: 0;
}

.hide-show {
  display: none;
}

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

<button class="toggle-year">&#9660;</button>
<div class="hide-show">
  Content comes here
</div>