Several Modal Images on page

Question

I'm new with JS, I'm trying to use 2 modal images on same page with this code:

https://www.w3schools.com/howto/howto_css_modal_images.asp

With this HTML, JS and CSS view resizing works only for one image, not sure how to make it work for two images on same page:

I have first html code two times for each image:

HTML:

<img id="myImg" src="img_fjords.jpg" alt="Trolltunga, Norway" width="300" height="200">
<div id="myModal" class="modal">
  <span class="close">&times;</span>
  <img class="modal-content" id="img01">
  <div id="caption"></div>
</div> 

CSS in big-picture.css:

#myImg {
    border-radius: 5px;
    cursor: pointer;
    transition: 0.3s;
}

#myImg:hover {opacity: 0.7;}

.modal {
    display: none; /* Hidden by default */
    position: fixed; /* Stay in place */
    z-index: 1; /* Sit on top */
    padding-top: 100px; /* Location of the box */
    left: 0;
    top: 0;
    width: 100%; /* Full width */
    height: 100%; /* Full height */
    overflow: auto; /* Enable scroll if needed */
    background-color: rgb(0,0,0); /* Fallback color */
    background-color: rgba(0,0,0,0.9); /* Black w/ opacity */
}

.modal-content {
    margin: auto;
    display: block;
    width: 80%;
    max-width: 700px;
}

#caption {
    margin: auto;
    display: block;
    width: 80%;
    max-width: 700px;
    text-align: center;
    color: #ccc;
    padding: 10px 0;
    height: 150px;
}

.modal-content, #caption {
    animation-name: zoom;
    animation-duration: 0.6s;
}

@keyframes zoom {
    from {transform:scale(0)}
    to {transform:scale(1)}
}

.close {
    position: absolute;
    top: 15px;
    right: 35px;
    color: #f1f1f1;
    font-size: 40px;
    font-weight: bold;
    transition: 0.3s;
}

.close:hover,
.close:focus {
    color: #bbb;
    text-decoration: none;
    cursor: pointer;
}

@media only screen and (max-width: 700px){
    .modal-content {
        width: 100%;
    }
} 

and JS:

var modal = document.getElementById('myModal');
var img = document.getElementById('myImg');
var modalImg = document.getElementById("img01");
var captionText = document.getElementById("caption");
img.onclick = function(){
    modal.style.display = "block";
    modalImg.src = this.src;
    captionText.innerHTML = this.alt;
}

var span = document.getElementsByClassName("close")[0];

span.onclick = function() {
  modal.style.display = "none";
} 

Answer 1

The code you have mostly works, but you're referencing specifically a single image. By using document.getElementById(), you haven't allowed for a second image. I've changed your code a little -- the HTML now has a few images for sample purposes and the JS now uses document.getElementsByClassName() to allow for multiple images. Further, I'm iterating over the list of images, and attaching that event handler to each one. See it as a fiddle, or here it is:

// create references to the modal...
var modal = document.getElementById('myModal');
// to all images -- note I'm using a class!
var images = document.getElementsByClassName('myImages');
// the image in the modal
var modalImg = document.getElementById("img01");
// and the caption in the modal
var captionText = document.getElementById("caption");

// Go through all of the images with our custom class
for (var i = 0; i < images.length; i++) {
  var img = images[i];
  // and attach our click listener for this image.
  img.onclick = function(evt) {
    modal.style.display = "block";
    modalImg.src = this.src;
    captionText.innerHTML = this.alt;
  }
}

var span = document.getElementsByClassName("close")[0];

span.onclick = function() {
  modal.style.display = "none";
}

#myImg {
  border-radius: 5px;
  cursor: pointer;
  transition: 0.3s;
}

#myImg:hover {
  opacity: 0.7;
}

.modal {
  display: none;
  /* Hidden by default */
  position: fixed;
  /* Stay in place */
  z-index: 1;
  /* Sit on top */
  padding-top: 100px;
  /* Location of the box */
  left: 0;
  top: 0;
  width: 100%;
  /* Full width */
  height: 100%;
  /* Full height */
  overflow: auto;
  /* Enable scroll if needed */
  background-color: rgb(0, 0, 0);
  /* Fallback color */
  background-color: rgba(0, 0, 0, 0.9);
  /* Black w/ opacity */
}

.modal-content {
  margin: auto;
  display: block;
  width: 80%;
  max-width: 700px;
}

#caption {
  margin: auto;
  display: block;
  width: 80%;
  max-width: 700px;
  text-align: center;
  color: #ccc;
  padding: 10px 0;
  height: 150px;
}

.modal-content,
#caption {
  animation-name: zoom;
  animation-duration: 0.6s;
}

@keyframes zoom {
  from {
    transform: scale(0)
  }
  to {
    transform: scale(1)
  }
}

.close {
  position: absolute;
  top: 15px;
  right: 35px;
  color: #f1f1f1;
  font-size: 40px;
  font-weight: bold;
  transition: 0.3s;
}

.close:hover,
.close:focus {
  color: #bbb;
  text-decoration: none;
  cursor: pointer;
}

@media only screen and (max-width: 700px) {
  .modal-content {
    width: 100%;
  }
}

<img class="myImages" id="myImg" src="http://onebigphoto.com/uploads/2012/10/midnight-sun-in-lofoten-norway.jpg" alt="Midnight sun in Lofoten, Norway" width="300" height="200">
<img class="myImages" id="myImg" src="http://cdn-image.travelandleisure.com/sites/default/files/styles/1600x1000/public/1490029386/fisherman-cabin-hamnoy-lofoten-islands-norway-NORWAY0320.jpg?itok=cpPuUjh1" alt="Fishermen's cabins in Lofoten, Norway"
width="300" height="200">
<img class="myImages" id="myImg" src="http://fjordtours.blob.core.windows.net/fjordtours-umbraco/1199/gerirangerfjord-per-ottar-walderhaug-fjordnorway.jpg" alt="Gerirangerfjord, Norway" width="300" height="200">
<div id="myModal" class="modal">
  <span class="close">&times;</span>
  <img class="modal-content" id="img01">
  <div id="caption"></div>
</div>