ช่วยตรวจสอบที่ครับว่าทำไมSlideไม่ยอมเลื่อนเอง ใส่ตัวกำหนดเวลาแล้วแต่ไม่ยอมเลื่อนไม่รู้ผมผิดตรงไหน

โครงครับ
<div class="slideshow-container">
                <div class="mySlides fade">
                    <a href="#"><img src="img/slide/test1.jpg" style="width:100%"></a>
                </div>
                <div class="mySlides fade">
                    <a href="#"><img src="img/slide/img_2.jpg" style="width:100%"></a>
                </div>
                <div class="mySlides fade">
                    <a href="#"><img src="img/slide/img_3.jpg" style="width:100%"></a>
                </div>
                <div class="mySlides fade">
                    <a href="#"><img src="img/slide/img_1.jpg" style="width:100%"></a>
                </div>
                    <a class="prev" onclick="plusSlides(-1)">&#10094;</a>
                    <a class="next" onclick="plusSlides(1)">&#10095;</a>
                <br>
                <div style="text-align:center">
                    <span class="dot" onclick="currentSlide(1)"></span> 
                    <span class="dot" onclick="currentSlide(2)"></span> 
                    <span class="dot" onclick="currentSlide(3)"></span>
                    <span class="dot" onclick="currentSlide(4)"></span>  
                </div>
                <script src="js/slidejs.js"></script>
                <table height="10"></table> 
            </div>

CSS
* {box-sizing: border-box}
body {font-family: Verdana, sans-serif; margin:0}
.mySlides {
    display: none;
    width:330px;
    height:300px;}
img{vertical-align: middle;}
.captionText{
    margin: 0;
}

/* Slideshow container */
.slideshow-container {
  position: relative;
  width: 100%;
  height: 350px;
  max-width: 350px;
  margin: auto;
  user-select: none;
  box-shadow: 0px 0px 3px 1px #00000078;
  padding: 10px;
  box-sizing: border-box;
  float: left;
}

/* Next & previous buttons */
.prev, .next {
  cursor: pointer;
  position: absolute;
  top: 50%;
  width: auto;
  padding: 16px;
  margin-top: -22px;
  color: white;
  font-weight: bold;
  font-size: 18px;
  transition: 0.6s ease;
  border-radius: 0 3px 3px 0;
  user-select: none;
}

/* Position the "next button" to the right */
.next {
  right: 0;
  border-radius: 3px 0 0 3px;
}

/* On hover, add a black background color with a little bit see-through */
.prev:hover, .next:hover {
  background-color: rgba(0,0,0,0.8);
}

/* Caption text */
.text {
  color: #f2f2f2;
  font-size: 15px;
  padding: 8px 12px;
  position: absolute;
  bottom: 8px;
  width: 100%;
  text-align: center;
}

/* Number text (1/3 etc) */
.numbertext {
  color: #f2f2f2;
  font-size: 12px;
  padding: 8px 12px;
  position: absolute;
  top: 0;
}

/* The dots/bullets/indicators */
.dot {
  cursor: pointer;
  height: 15px;
  width: 15px;
  margin: 0 2px;
  background-color: #bbb;
  border-radius: 50%;
  display: inline-block;
  transition: background-color 0.6s ease;
}

.active, .dot:hover {
  background-color: #717171;
}

/* Fading animation */
.fade {
  -webkit-animation-name: fade;
  -webkit-animation-duration: 1.5s;
  animation-name: fade;
  animation-duration: 1.5s;
}

@-webkit-keyframes fade {
  from {opacity: .4} 
  to {opacity: 1}
}

@keyframes fade {
  from {opacity: .4} 
  to {opacity: 1}
}

/* On smaller screens, decrease text size */
@media only screen and (max-width: 300px) {
  .prev, .next,.text {font-size: 11px}
}

JS
var slideIndex = 1;
showSlides(slideIndex);

// Next/previous controls
function plusSlides(n) {
  showSlides(slideIndex += n);
}

// Thumbnail image controls
function currentSlide(n) {
  showSlides(slideIndex = n);
}

function showSlides(n) {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var dots = document.getElementsByClassName("dot");
  if (n > slides.length) {slideIndex = 1} 
  if (n < 1) {slideIndex = slides.length}
  for (i = 0; i < slides.length; i++) {
      slides[i].style.display = "none"; 
  }
  for (i = 0; i < dots.length; i++) {
      dots[i].className = dots[i].className.replace(" active", "");
  }
  slides[slideIndex-1].style.display = "block"; 
  dots[slideIndex-1].className += " active";
}
var slideIndex = 0;
showSlides();

function showSlides() {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  for (i = 0; i < slides.length; i++) {
    slides[i].style.display = "none"; 
  }
  slideIndex++;
  if (slideIndex > slides.length) {slideIndex = 1} 
  slides[slideIndex-1].style.display = "block"; 
  setTimeout(showSlides, 2000); // Change image every 2 seconds
}