JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="watched_textarea" rows="10" cols="45">assdsddsds

ssdsa</textarea>
<div id="output_div"></div>

JavaScript

function nl2br_js(myString) {
var regX = /\n/gi ;

s = new String(myString);
s = s.replace(regX, "<br /> \n");
return s;
}

$( "#watched_textarea" ).keyup( function() {
       $( "#output_div" ).html( nl2br_js($( this ).val()) );
    });