JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="content_plot"></textarea>
    <div id="counter"><span>350</span> characters remaining.</div>

CSS

* { font: normal 12px/22px arial; }

textarea {
   width:400px;
   height:200px;
   border:1px solid #999;
   border-radius:3px;
   padding:7px;
}

#counter span { font-weight:700 }

JavaScript

$('textarea').keyup(function(){
    ta = $(this);
    if(ta.val().length >= 350){
        ta.val( ta.val().substr(0, 350) );
    } else {
        $("#counter span").text(350-ta.val().length);
    }
});

setInterval('$("#counter span").text(350-ta.val().length);', 350);