JSFiddle - React, Tailwind, and code Playground

HTML

<div id="in">Click here and type to edit.</div>

CSS

div { 
    border:1px solid #AEAEAE; 
    width: 250px; }

JavaScript

$(function() {
    var $in = $("#in"),
        w = $in.width();
    $in.css("font-size", 20*30/$in.text().length);
    $in.click(function() {
        this.contentEditable='true';
    });
    $(document).keyup(function() {
        $in.css("font-size", 20*30/$in.text().length);
    });
});