JSFiddle - React, Tailwind, and code Playground

by ricardobchaves6

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<form action="" method="post">
<select class="form-control" id="options" name="options" multiple="multiple">
    <option value="1">Opção 1</option>
    <option value="2">Opção 2</option>
    <option value="3">Opção 3</option>
    <option value="4">Opção 4</option>
    <option value="5">Opção 5</option>
    <option value="6">Opção 6</option>
    <option value="7">Opção 7</option>
    <option value="8">Opção 8</option>
    <option value="9">Opção 9</option>
    <option value="10">Opção 10</option>
</select>
<input type="submit" id="send" name="send" value="enviar">
</form>

JavaScript

$( "#send" ).click(function() {
  var count = $("#options :selected").length;
  alert( count );
});