Javascript Slideshow Image Container

So here is my code. I so far have the slide show worker with said given images.

The problem I am having is Containing + Stretching the images to fit inside of my container div. 🙂

Here is the code:

All help is welcome~! Thanks. ^^

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
}
.imgContainer {
    padding-top: 80px;
    background-color: rgba(0, 0, 0, 0.603);
    width: 100%;
    height: 575px;
}

.img1 {
    max-width: 100%;
    max-height: 100%;
    object-fit: cover; 
}
<div class="imgContainer" alt="imgContainer">
<img class="mySlides" src="/Users/stevenjeffers/Documents/GitHub/III/images/1.jpg" alt="imgj1">
<img class="mySlides" src="/Users/stevenjeffers/Documents/GitHub/III/images/2.jpg" alt="imgj1">
<img class="mySlides" src="/Users/stevenjeffers/Documents/GitHub/III/images/3.jpg" alt="imgj1">

</div>