JSFiddle - React, Tailwind, and code Playground

HTML

<input  size="5" style="font-family:Courier"; onkeyup="Expand(this);">

CSS

*{font-size:14px}

JavaScript

function Expand(obj){
      if (!obj.savesize) obj.savesize=obj.size;
      obj.size=Math.max(obj.savesize,obj.value.length);
     }