JSFiddle - React, Tailwind, and code Playground

HTML

<div class="fb-Search">
  <input id="Input" class="fb-Search_Input" value="">
  <span class="fb-Search_FauxInput" dir="rtl"></span>
  <label class="fb-Search_Label" for="Input">Search</label>
</div>

CSS

* {
  box-sizing: border-box;
}

body {
  background-color: #555;
  font-family: sans-serif;
}

.fb-Search {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  height: 44px;
  padding: 5px 70px 5px 5px;
  width: 400px;
  position: relative;
  background-color: #e4e4e4;
}

.fb-Search_Input {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
}

.js .fb-Search_Input {
  position: absolute;
  left: -100vw;
}

.fb-Search_FauxInput {
  display: none;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
  max-width: 80%;
  margin-top: 14px;
  border: 0;
  font-size: 20px;
  font-size: 1.3rem;
  color: #777;
  background-color: #e4e4e4;
  border-right: 3px solid transparent;
  height: 3px;
}

.js .fb-Search_FauxInput {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
}

.fb-Search_Input:focus ~ .fb-Search_FauxInput {
  -webkit-animation: pulseAttention 1.5s cubic-bezier(.215, .61, .355, 1) forwards infinite;
  animation: pulseAttention 1.5s cubic-bezier(.215, .61, .355, 1) forwards infinite;
}

.fb-Search_Label {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  padding: 5px;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
  color: #a7a7a7;
  font-size: 15px;
}

.fb-Search_Input:not([value=""]) ~ .fb-Search_Label {
  -webkit-box-pack: end;
  -ms-flex-pack: end;
  justify-content: flex-end;
}

@-webkit-keyframes pulseAttention {
  50% {
    border-color: green;
  }
}

@keyframes pulseAttention {
  50% {
    border-color: green;
  }
}

JavaScript

document.documentElement.setAttribute("class", "js");

var searchFauxInput = document.querySelector(".fb-Search_FauxInput");
var searchBox = document.getElementById("Input");

searchBox.addEventListener("keyup", function copyInput(event) {
  searchFauxInput.textContent = searchBox.value;
  searchBox.setAttribute("value", searchBox.value);
}, false);

searchBox.focus();