JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" />

JavaScript

$(function(){
    $("input").keyup(function(){
       var $this = $(this);
        if ($this.val().indexOf("=")>=0){
           $this.val(eval($this.val().replace("=", "").replace("x","*")));
        }            
    });
});