JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">
<textarea name="" id="area" maxlength="100"></textarea>
<div class="word-counter">0/100</div>
</div>

CSS

.box {
width:500px;
border: 1px solid red;
position:relative;
display:table;
}
textarea {
width:500px;
height:80px;
padding-bottom: 20px;
}
.word-counter {
position:absolute;
bottom: 0;
right:0;
}

JavaScript

$('#area').keyup(function(){
    $('.word-counter').text(this.value.length+'/100');
})