JSFiddle - React, Tailwind, and code Playground

HTML

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<img src="https://image.ibb.co/eQFRx7/post_2852_0_65714800_1522594854_thumb.png" alt="image"/>
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<div style="background:#333;height:300px">
<p>
The footer
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CSS

img{position:fixed;left:10px;top:10%}

JavaScript

window.onscroll = function(ev) {
    if ((window.innerHeight + window.scrollY) >= document.body.offsetHeight) {
        alert("you're at the bottom of the page");
    }
};