JSFiddle - React, Tailwind, and code Playground

HTML

<div class="exists"> </div>

JavaScript

//duck-punched
$.fn.is = (function(is){
    return function(){
        if(arguments.length === 0) return this.length > 0;
        return is.apply(this, arguments);        
    };
})($.fn.is);


$('<div/>').text('.exists exists? ' + $('.exists').is()).appendTo('body');

$('<div/>').text('.does-not-exist exists? ' + $('.does-not-exist').is()).appendTo('body');

$('<div/>').text('.exists is .exists? ' + $('.exists').is('.exists')).appendTo('body');