JSFiddle - React, Tailwind, and code Playground

HTML

<form onsubmit="return validateForm()">
  <input type="text" value="" id="title_input" />
  <input type="submit"  />
</form>

JavaScript

function validateForm() {
	var titleEl = document.getElementById('title_input');
  var title = titleEl.value;
  var upperLength = 0;
  
  for (var i = 0; i < title.length; i++) {
  	upperLength += (title[i] === title[i].toUpperCase() ? 1 : 0);
  }
  
  if (upperLength === title.length) {
  	alert('Invalid title');
    return false;
  }
  
  return true;
};