JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <img class="slideshow" src="slideshow/pictures/Background.jpg" />
</body>

JavaScript

$(document).ready(function() {
    var pictureNames = getPictureList();
    slideShow(0, pictureNames);
});

function getPictureList(pictureNames) {
    $.ajax({
        type: "GET",
        url: "slideshow/get_files.php",
        cache: false,
        success: function(result){
            pictureNames = result.split(':');
            return pictureNames;
        }
    });
}

function slideShow(slideNumber, pictureNames) {
    $('.slideshow').attr('src',"slideshow/pictures/"+pictureNames[slideNumber]);
    if (slideNumber==pictureNames.size) {
        slideNumber=0;
    }
    setTimeout(slideShow(++slideNumber, pictureNames), 5000);
}