demo.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    div {
        height: 100%;
        width: 100%;
        border: 1px solid springgreen;
        font-size: 3em;
        position: absolute;
        top: 0;
        left: 0;
        transition: 1.2s;
    }

    main {
        position: relative;
        overflow: hidden;
        width: 500px;
        height: 300px;
    }
</style>
<body>
    <main>
            <div>1</div>
            <div>2</div>
            <div>3</div>
            <div>4</div>
            <div>5</div>
    </main>

</body>
<script charset="UTF-8" src="slider.js"></script>
</html>