Function is not defined node.js Uncaught Reference error

In my app.js file I defined a function like this:

function testfunc() {
    console.log("Testing");
}

And in my home.html file I have this:

<script type="text/javascript" src="./app.js"></script>

<div class="ProfileImage" onmouseover="testfunc()"> </div>

but when I mouseover the div it produces this

Uncaught ReferenceError: testfunc is not defined

Here is my file structure:

from Function is not defined node.js Uncaught Reference error