JSFiddle - React, Tailwind, and code Playground

HTML

<fieldset>
  <h2 class="title">//Javascript</h2>
  <input type="text" id="input" placeholder="Digite alguma coisa:">
  <label for="input" id="result">Resultado: <span id="result-text"></span></label>
</fieldset>

<fieldset>
  <h2 class="title">//jQuery</h2>
  <input type="text" id="input-jquery" placeholder="Digite alguma coisa:">
  <label for="input" id="result-jquery">Resultado: <span id="result-text-jquery"></span></label>
</fieldset>

CSS

* {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  box-sigin: border-box
}

.title {
  margin-bottom: 10px;
}

fieldset {
  margin: 15px;
  padding: 15px;
  border: 1px solid #CACACA
}

label,
input {
  display: block
}

input {
  margin-bottom: 10px;
  padding: 5px;
}

JavaScript

//Javascript
var result_text = document.getElementById('result-text');
document.getElementById('input').addEventListener('keyup', function() {
	result_text.innerHTML = this.value
});

//jQuery
var result_text_jquery = $('#result-text-jquery');
$('#input-jquery').on('keyup', function() {
  result_text_jquery.html(this.value)
})