JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" value="abcdde">
<pre></pre>

JavaScript

let validate = function(evt) {
	let str = evt.target.value;
  let isUnique = /(.).*\1/.test(str);
  
  console.log(str, isUnique);
  document.querySelector('pre').innerHTML += `${str} ${isUnique}\n`;
}

document.querySelector('input').addEventListener('keyup', validate)