JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="index.css">

    <title>Document</title>
    <div id="div_one"></div>
    <div id="div_two"></div>
</head>
<body>
    <script src="index.js"></script>
</body>
</html>

CSS

#div_one {
    width: 50px; 
    height: 50px;
    border: 10px solid red;
}

#div_two {
    width: 50px; 
    height: 50px;
    border: 10px solid blue;
}

@keyframes move {
    100% {
        transform: translateX(300px);;
    }
}
@keyframes down {
    100% {
        transform: translateY(300px);;
    }
}

JavaScript

let move_boxes = () => {
    return new Promise( (resolve, reject) => {
        resolve ('boxes moved!')
    })
};
let move_box_one = () => {
    return new Promise( (resolve, reject) => {
        document.getElementById('div_two').style.animation = 'move 3s forwards';
        setTimeout(()=> resolve(), 3000);   
    })

}
let move_box_two = () => {
    return new Promise( (resolve, reject) => {
        document.getElementById('div_one').style.animation = 'move 3s forwards';
        setTimeout(()=> resolve(), 3000);
    })
}

move_boxes().then(() => {
    return move_box_one();
}).then(() => {
    return move_box_two();
});