JSFiddle - React, Tailwind, and code Playground

HTML

<img alt="mainIMG" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Cat_tail_ani.gif/40px-Cat_tail_ani.gif" id="mainIMG"/>
<img alt="imgThumb1" src="http://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Dog_silhouette.svg/50px-Dog_silhouette.svg.png" />

JavaScript

$(document).ready(function(){
    $('img[alt="imgThumb1"]').click(function(){
        var trial = $('img[alt="imgThumb1"]').attr('src');
        $('img[alt="mainIMG"]').attr("src", trial);
    });
});