JSFiddle - React, Tailwind, and code Playground

HTML

<a href="#">1</a>
<a href="#">2</a>
<a href="#">3</a>
<a href="#">4</a>
<a href="#">5</a>

JavaScript

Slick.definePseudo('divisible-by', function(n){
  return (parseInt(this.innerHTML, 10) % parseInt(n, 10) == 0);
});

var length = $$(':divisible-by(1)').length;
log('found '+length+' elements that are divisible by 1');


var length = $$(':divisible-by(2)').length;
log('found '+length+' elements that are divisible by 2');


var length = $$(':divisible-by(3)').length;
log('found '+length+' elements that are divisible by 3');


function log(text){
    new Element('div', {html: text}).inject(document.body);
}