html select placeholder

Placeholder attribute does not exist for the <select> tag.
But there are some ways to make a placeholder for the select box.
The easiest way of making a placeholder for the <select> element is using the disabled and selected attributes with the HTML5 hidden global attribute.
  
<select name="monthname" required>
  <option value="" selected disabled hidden>Select Month</option>
  <option value="Jan">January</option>
  <option value="Feb">February</option>
  <option value="Mar">March</option>
  <option value="Apr">April</option>
  <option value="May">May</option>
  <option value="Jun">June</option>
  <option value="Jul">July</option>
  <option value="Aug">August</option>
  <option value="Sep">September</option>
  <option value="Oct">October</option>
  <option value="Nov">November</option>
  <option value="Dec">December</option>
</select>

<form action="/action_page.php">
	<label for="phone">Enter a phone number:</label>
    <input type="tel" id="phone" name="phone" placeholder="123-45-678" pattern="[0-9]{3}-[0-9]{2}-[0-9]{3}"><br><br>
 </form> 
 

$(".js-example-placeholder-single").select2({
    placeholder: "Select a state",
    allowClear: true
});

<option value="" selected disabled hidden>Select Here</option>

select