Why when I click on the second image it doesn't pop up as the first one?

Question

I been trying to figure out how to make the second image appear with the effect of pop up when I click on it. the second image has exactly the same code of the first, and even with that doesn't make the same pop-up effect. I'm sorry for my bad English I'm from Japan, I would appreciate some help guys.

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

#myImg:hover {opacity: 0.7;}

/* The Modal (background) */
.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 (image) */
.modal-content {
    margin: auto;
    display: block;
    width: 80%;
    max-width: 700px;
}

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

/* Add Animation */
.modal-content, #caption {    
    -webkit-animation-name: zoom;
    -webkit-animation-duration: 0.6s;
    animation-name: zoom;
    animation-duration: 0.6s;
}

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

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

/* The Close Button */
.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;
}

/* 100% Image Width on Smaller Screens */
@media only screen and (max-width: 700px){
    .modal-content {
        width: 100%;
    }
}

<h2>Image Modal</h2>
<p>In this example, we use CSS to create a modal (dialog box) that is hidden by default.</p>
<p>We use JavaScript to trigger the modal and to display the current image inside the modal when it is clicked on. Also note that we use the value from the image's "alt" attribute as an image caption text inside the modal.</p>

<img id="myImg" src="https://cdn.theatlantic.com/assets/media/img/mt/2017/06/GettyImages_675371680/lead_960.jpg?1498239007" alt="Trolltunga, Norway" width="300" height="200">

<img id="myImg" src="https://cdn.theatlantic.com/assets/media/img/mt/2017/06/GettyImages_675371680/lead_960.jpg?1498239007" alt="Trolltunga, Norway" width="300" height="200">

<!-- The Modal -->
<div id="myModal" class="modal">
  <span class="close">&times;</span>
  <img class="modal-content" id="img01">
  <div id="caption"></div>
</div>


<script>
// Get the modal
var modal = document.getElementById('myModal');

// Get the image and insert it inside the modal - use its "alt" text as a caption
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;
}

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks on <span> (x), close the modal
span.onclick = function() { 
    modal.style.display = "none";
}
</script>

Answer 1

You should never set the same ID in different elements. The ID should be unique. When you are using var img = document.getElementById('myImg'); You are only selecting the first element.

Solution

One way you can do it is setting the same class to both elements.

<img class="images" id="myImg" src="https://cdn.theatlantic.com/assets/media/img/mt/2017/06/GettyImages_675371680/lead_960.jpg?1498239007" alt="Trolltunga, Norway" width="300" height="200"> 
<img class="images" id="myImg" src="https://cdn.theatlantic.com/assets/media/img/mt/2017/06/GettyImages_675371680/lead_960.jpg?1498239007" alt="Trolltunga, Norway" width="300" height="200">

Now you can get both elements with getElementsByClassName.

You will get an HTML Collection so you need to parse it to an Array.

var imagesCollection = document.getElementsByClassName('images');
var imagesArray = Array.prototype.slice.call( imagesCollection );

Last step is give it a name to the onclick handler so you can set it in both elements with map

function imageOnClickHandler(){
  modal.style.display = "block";
  modalImg.src = this.src;
  captionText.innerHTML = this.alt;
}

imagesArray.map(function (img){
  img.onclick = imageOnClickHandler;
})

Full Source Code

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

#myImg:hover {opacity: 0.7;}

/* The Modal (background) */
.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 (image) */
.modal-content {
    margin: auto;
    display: block;
    width: 80%;
    max-width: 700px;
}

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

/* Add Animation */
.modal-content, #caption {
    -webkit-animation-name: zoom;
    -webkit-animation-duration: 0.6s;
    animation-name: zoom;
    animation-duration: 0.6s;
}

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

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

/* The Close Button */
.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;
}

/* 100% Image Width on Smaller Screens */
@media only screen and (max-width: 700px){
    .modal-content {
        width: 100%;
    }
}

<h2>Image Modal</h2>
<p>In this example, we use CSS to create a modal (dialog box) that is hidden by default.</p>
<p>We use JavaScript to trigger the modal and to display the current image inside the modal when it is clicked on. Also note that we use the value from the image's "alt" attribute as an image caption text inside the modal.</p>

<img class="images" id="myImg" src="https://cdn.theatlantic.com/assets/media/img/mt/2017/06/GettyImages_675371680/lead_960.jpg?1498239007" alt="Trolltunga, Norway" width="300" height="200">

<img class="images" id="myImg" src="https://cdn.theatlantic.com/assets/media/img/mt/2017/06/GettyImages_675371680/lead_960.jpg?1498239007" alt="Trolltunga, Norway" width="300" height="200">
<link rel="stylesheet" href="/playground/modal.css">
<!-- The Modal -->
<div id="myModal" class="modal">
  <span class="close">&times;</span>
  <img class="modal-content" id="img01">
  <div id="caption"></div>
</div>


<script>
// Get the modal
var modal = document.getElementById('myModal');

// Get the image and insert it inside the modal - use its "alt" text as a caption
var imagesCollection = document.getElementsByClassName('images');
var imagesArray = Array.prototype.slice.call( imagesCollection )

var modalImg = document.getElementById("img01");
var captionText = document.getElementById("caption");

imagesArray.map(function (img){
  img.onclick = imageOnClickHandler;
})


function imageOnClickHandler(){
  modal.style.display = "block";
  modalImg.src = this.src;
  captionText.innerHTML = this.alt;
}

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks on <span> (x), close the modal
span.onclick = function() {
    modal.style.display = "none";
}
</script>

Answer 2

Both image has same id that is myImg which is wrong id should be unique change it to class and use document.querySelectorAll instead of

document.getElementById

Answer 3

document.getElementById can only select one element at a time, you should use unique id for element.

For this one, one thing you wanna try out is add class="imgs" for your img elements, and use selector functions like document.querySelectorAll or document.getElementsByClassName. Then you can apply styles for each image by a for loop.