JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div class="my-div">My Div</div>
</div>

<br />

<div id="output">
</div>

CSS

#container {
    display: none;
}

.my-div {
    display: block;
    width: 100px;
    margin-left: 10px;
}

JavaScript

// Output : 100
$('<p>').html('Width without margins = ' + $('.my-div').outerWidth()).appendTo('#output');

// Output : 10, should be 110 ?
$('<p>').html('Width with margins = ' + $('.my-div').outerWidth(true)).appendTo('#output');