JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<li class="exam_li"><img id="picture" src="https://www.w3schools.com/css/img_fjords.jpg" alt="Slika Testa" width="60" height="60" class="img-resposive exam-img"></li>

<div id="imgmodal">
<div id="caption"><a id="download-link" download><span class="glyphicon glyphicon-download"></span><a id="download-link" download></a></div>
  <span id="close">&times;</span>
  <img class="content" id="img">

CSS

.exam-img:hover {
	cursor: pointer;
	transition: 0.2s;
	overflow: hidden;
}

/* exam_img */
#imgmodal {
    display: none; 
    position: fixed; 
    z-index: 1; 
    padding-top: 80px; 
    left: 0;
    top: 0;
    width: 100%;
    height: 100%; /* Full height */
    background-color: rgb(0,0,0); /* Fallback color */
    overflow: auto;
    background-color: rgb(0,0,0); /* Black w/ opacity */
    transition: 0.3s;
}

/* Modal Content (image) */
.content {
	margin: auto;
    display: block;
    height: 90%;

}

/* Caption of Modal Image */
#caption {
    text-align: center;
    color: #ccc;
    position: absolute;
    top: 15px;
    left: 35px;
    font-size: 40px;
    margin-top: 0;
}

/* Add Animation */
.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: 100;
    transition: 0.3s;
}

#close:hover,
#close:focus {
    color: #989898;
    text-decoration: none;
    cursor: pointer;
}
#download-link{
	font-size: 25px;
	color: #f1f1f1;
	font-weight: normal;
	text-decoration: none;
	transition: 0.2s;
	padding: 10px;
}
#download-link:hover {
	color: #989898;
}

/* 100% Image Width on Smaller Screens */
@media only screen and (max-width: 768px){
    .content {
    	width: 100%;
    	max-height: 90%;
    	height: auto;
    }
    #close {
    top: 2px;
    font-size: 40px;
    }
    #imgmodal {
    	padding-top: 50px;
    }
    #caption {
    	top: -1px;
    }
}

JavaScript

var modal = document.getElementById('imgmodal');
var img = document.getElementById('picture');
var modalImg = document.getElementById("img");
var download = document.getElementById('download-link');
img.onclick = function(){
    modal.style.display = "block";
    modalImg.src = this.src;
    download.href = this.src;
}
var span = document.getElementById("close");
span.onclick = function() { 
    modal.style.display = "none";
}