<div class="dropdown">
  <div class="form">
    <input type="text" id="select" value="--- select ---">
    <button class="button"> <i class="fas fa-chevron-down fa-sm"></i></button>
  </div>
  <ul class="dropdownList">
    <li><a href="#">option one</a></li>
    <li><a href="#">option two</a></li>
  </ul>
 </div>
* {
  box-sizing: border-box;
}

a {
  text-decoration: none;
  color: #fff;
}

//layout
.dropdown {
  width: 220px;
  height: auto;
  display: flex;
  flex-direction: column;
  .form {
    display: flex;
    input {
      width: 200px;
    }
    .button {
      width: 50px;
      .fa-chevron-down {
        transform: rotate(0deg);
        transition: all 0.6s;

        &.active {
          transform: rotate(180deg);
        }
      }
    }
    input,
    button {
      border: none;
      padding: 20px 5px;
      background-color: black;
      color: #fff;
      cursor: pointer;
      &:focus {
        outline: none;
      }
    }
  }
  .dropdownList {
    display: none;
    background-color: #000;
    li {
      padding: 20px;
      &:hover {
        background-color: #333333;
        transition: all 0.5s ease;
      }
    }
  }
}
View Compiled
$(function () {
  $(".button").click(function (e) {
    e.preventDefault();
    $(".dropdownList").slideToggle(500);
    $(".fa-chevron-down").toggleClass("active");
  });
});

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.13.0/css/all.min.css

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.min.js