JSFiddle - React, Tailwind, and code Playground

HTML

<div style="width:600px">My text string here.</div>

CSS

div { border: 1px #000 solid; }

JavaScript

$.fn.resizeText = function(){
      var size = parseInt($(this).css("fontSize"));  
      var html = $(this).html();
      var textLength = html.length;
      var span = '<span>' + html + '</span>';
      $(this).html(span);
      var width = $(this).find('span:first').width();
      $(this).html(html);
      var newSize = $(this).width()/width*size; 
      $(this).css("fontSize", newSize);
      return width;
    };

$("div").resizeText();