JSFiddle - React, Tailwind, and code Playground

HTML

<form>
  <fieldset>
  <legend>Input ordinate :</legend>
  <input type="text" id="ordinateId" name="input"/>
  <input type="button" id="startbuttonId" value="Start particle"/>
  </fieldset> 
</form>

JavaScript

var button = document.getElementById("startbuttonId");

button.onclick = function() {
  var value = document.getElementById("ordinateId").value;
  console.log(value);
}