p>

<p class="source">
    Source: <a target="_blank" href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Closures/">MDN - Closures</a>
</p>

<h3>Strict mode</h3>

<p>
    ECMAScript 5's strict mode is a way to opt in to a restricted variant of JavaScript. Strict mode isn't just a subset: it intentionally has different semantics from normal code. Browsers not supporting strict mode will run strict mode code with different behavior from browsers that do, so don't rely on strict mode without f