eature-testing for support for the relevant aspects of strict mode. Strict mode code and non-strict mode code can coexist, so scripts can opt into strict mode incrementally.
 </p>

<p class="source">
    Source: <a target="_blank" href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions_and_function_scope/Strict_mode/">MDN - Strict mode</a>
</p>

<h3>Immediately-Invoked Function Expression (IIFE)</h3>

<p>
   An immediately-invoked function expression is a pattern which produces a l