JSFiddle - React, Tailwind, and code Playground

HTML

<textarea placeholder='This is a line \n this should be a new line'></textarea>
<textarea id="textarea1"></textarea>
<textarea id="textarea2"></textarea>
<textarea id="textarea3"></textarea>
<textarea id="textarea4"></textarea>

CSS

textarea{
    width:300px;
    height:100px;
}

JavaScript

$('#textarea1').val('hello' + '\n' + 'world');
$('#textarea2').attr('placeholder', 'hello' + '\n' + 'world');
$('#textarea3').attr('placeholder', 'hello' + '\u000A\u000D' + 'world');
$('#textarea4').attr('placeholder', 'hello' + '&#13;&#10;' + 'world');