JSFiddle - React, Tailwind, and code Playground

HTML

<button class="ty-pict">Click</button>
<div class="mfp-content">
    <figure>
        <img src="http://dcoder.eu/wp-content/uploads/2015/09/tabbed_content_box_02.png" />
    </figure>
</div>

CSS

.mfp-img {
    -webkit-user-select: none;  /* Chrome all / Safari all */
    -moz-user-select: none;     /* Firefox all */
    -ms-user-select: none;      /* IE 10+ */
    -o-user-select: none;
    user-select: none;
}

JavaScript

$(".ty-pict").on("click", function () {
    $(".mfp-content figure img").addClass("mfp-img");
});