JSFiddle - React, Tailwind, and code Playground

HTML

<div>div one</div>
<div>div two</div>

JavaScript

jQuery.fn.findOne = function( selector ) {
   var result = this.find( selector );
   if ( result.length != 1 ) {
      //jQuery.error( "Didn't find one " + selector );
      alert( "Didn't find one " + selector + ", found " + result.length );
   }
   return this.pushStack( result );
};

$("body").findOne("div");