JSFiddle - React, Tailwind, and code Playground

HTML

<input id="freddy" style="width: 300px; height: 100px;" value="dasd">
<div id="susan"></div>

JavaScript

var max = 1000;

document.getElementById('freddy').onkeypress =
document.getElementById('freddy').onkeyup = 
document.getElementById('freddy').onkeydown = function(){
    var count = this.value.length;
    if(max < count){
        this.value = this.value.substring(0,999);
        return false;
    }
    setTimeout(function(){
        document.getElementById('susan').innerHTML =
          (max-count)+' characters left!';
    },1);
};