Remove duplicate record from Array in Angular using JavaScript and jQuery

I'm facing an issue. i have a dropdown contains list of users fetching from database. When i select a user from dropdown it appends and when i select the same user again it again appends as a new row.

So i want to stop duplicating same user.

Here's my View Code

<div class="form-group col-md-4 " style="display:none" id="user-container">
    <label>User</label>
    <select id="users" class="form-control" disabled="disabled">
        <option value="">Select User</option>
    </select>
    <p class="validate-error"><span id="users_error"></span></p>
</div>

Here's my JavaScript Code

PostMyData(obj, '/Admin/Meetings/GetUserGroupUsers', (res) => {
   
  if (res.Code === 0 || res.Code === -1) {
    alert(res.Message);
  }
  if (res.Code === 1) {
 
    $('#users').html('');
 
    $('#users').append('<option value="">Select User</option>');
 
    res.Data.map(item => {
      $('#users').append('<option value="${item.UserId}">${item.FirstName} ${item.LastName}</option>');
    });
 
    $('#users').prop('disabled', false);
  }
 
});