JSFiddle - React, Tailwind, and code Playground

HTML

<button id="left">&laquo;</button> <button id="right">&raquo;</button>
<div class="block"></div>

CSS

div { 
    position:absolute; 
    background-color:#abc; 
    left:50px;
    width:90px; 
    height:90px;
    margin:5px; 
}

JavaScript

$("#right").click(function() {
    $(".block").animate({
        "left": "+=50px"
    }, "slow", function() {
        animationCallback1();
    });
});

$("#left").click(function() {
    $(".block").animate({
        "left": "-=50px"
    }, "slow", function() {
        animationCallback2();
    });
});


function animationCallback1() {
    alert($(".block").is(':animated'));
}

function animationCallback2() {
    setTimeout(function() { alert($(".block").is(':animated')) }, 0);
}