problem with settimeout function in slideshow speeding up after about 5 interations

The following code I have implemented for a javascript slideshow appears to speed up after about 5 iterations, from once every 15 seconds to what appears to be about 1 second between transitions. Is there something wrong with how the jquery/javascript implements the setTimeout?

var images = new Array(
  'https://via.placeholder.com/150/0000FF',
  'https://via.placeholder.com/150/FF00FF',
  'https://via.placeholder.com/150/00FFFF',
  'https://via.placeholder.com/150/FFFF00',
  'https://via.placeholder.com/150/FF0000',
  'https://via.placeholder.com/150/00FF00',
  'https://via.placeholder.com/150/0000FF',
);
var nextimage = 0;

$(document).ready(function() {
  doSlideshow();
})

function doSlideshow() {
  if ($('.slideshowimage').length != 0) {
    $('.slideshowimage').fadeOut(500, function() {
      slideshowFadeIn();
      $(this).remove()
    });
  } else {
    slideshowFadeIn();
  }
}

function slideshowFadeIn() {
  if ($('.slideshow').length) {
    $('.slideshow').prepend($('<img class="slideshowimage" src="' + images[nextimage++] + '" style="display:none">').fadeIn(500, function() {
      setTimeout(doSlideshow, 15000);
    }));
  }
  if (nextimage >= images.length) {
    nextimage = 0;
  }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="slideshow">
</div>

Thanks

Answer

Use setInterval instead. You are currently adding new setTimeouts for every loop

I changed the speed to not have to wait 15 seconds

I also shortened the code and after spending far too long trying to figure out why the blue image showed twice, I removed one of the TWO blue pictures

var images = new Array(
  'https://via.placeholder.com/150/0000FF',
  'https://via.placeholder.com/150/FF00FF',
  'https://via.placeholder.com/150/00FFFF',
  'https://via.placeholder.com/150/FFFF00',
  'https://via.placeholder.com/150/FF0000',
  'https://via.placeholder.com/150/00FF00',
);
var nextimage = 0;

$(function() {
  slideshowFadeIn();
  setInterval(doSlideshow, 1500)
})

function doSlideshow() {
  $('.slideshowimage').fadeOut(500, function() {
    $(this).remove();
    slideshowFadeIn();
  });
}

function slideshowFadeIn() {
  nextimage = nextimage%images.length; // infinite
  $('.slideshow')
    .prepend($(`<img class="slideshowimage" src="${images[nextimage++]}" style="display:none">`)
      .fadeIn(500))
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="slideshow"></div>