JSFiddle - React, Tailwind, and code Playground

by Eugen Sunic

HTML

First name: <input id="first" type="text" name="FirstName" value=""><br>
<button id="btn">
Submit
</button>

JavaScript

var x;
x = document.getElementById("first").value;
document.getElementById('btn').addEventListener('click', function(event) {
  // do something
  x = document.getElementById("first").value;
  if (x < 0) {
    alert("validation red error");

  } else if (x > 800) {
    alert("validation red error");
  } else if (x >= 0 && x <= 800) {
    alert("good value input");
  }


});