var button = document.getElementById("submitsend")

button.onclick = async function() {
  var input = document.getElementById("userinput")
  input.value = ""
  var output = document.getElementById("output")
  $.getJSON("https://api.eriner.repl.co/fun/8ball", function(data) {
    console.log(data)
  })
}

<link rel="stylesheet" href="https://easycss.bookie0.repl.co/dark.css">

<nav>
  <h1>Hello</h1>
</nav>
<div class="content">
  <p id="output">Ask me anything.</p>
  <form onsubmit="return false" id="formm">
    <input id="userinput" placeholder="Say something." type="text">
    <button type="button" id="submitsend">Send</button>
  </form>
</div>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>