JSFiddle - React, Tailwind, and code Playground
HTML
<div id="destaques">
<div class="banner"><img src="images/001.jpg"/></div>
<div class="banner"><img src="images/002.jpg"/></div>
<div class="banner"><img src="images/003.jpg"/></div>
</div>
JavaScript
function bannerRotator(element) {
// Conta quantos banners existem:
i = 0;
$(element).find(".banner").each(function() {
i++;
$(this).addClass("test");
});
alert(i);
//
}
bannerRotator('#destaques');