JSFiddle - React, Tailwind, and code Playground

HTML

<div class="cair"></div>

CSS

.cair {
    position: absolute;
    top: 0px;
    padding: 30px;
    height: 50px;
    width: 50px;
    background-color: #ccf;
}

JavaScript

$(function () {
    var inicio;
    var fim = 385;
    $(".cair").animate({
        top: fim + "px",
    }, {
        duration: 6000,
            "complete": function () {
            $('.cair').remove();
        },
        start: function () {
            inicio = window.getComputedStyle(this).top.replace('px', '');

        },
        progress: function (a, p, r) {
            var valorAtual = p * (fim - inicio);
            if (Math.round(valorAtual) == 200) alert('chegámos aos 200px!');
        }
    });
});