Often I discover projects that are still in v2, and no words about v3 on their roadmap.<p>Maybe v4 should learn from JavaScript5 and Visual Basic 3-6.<p>Support v2 syntax out of the box using a (slow) shim layer if there is no<p><pre><code>  &quot;use strict&quot;
</code></pre>
in the first line. If that statement is present, don&#x27;t load the shim layer and support only v4 syntax (faster).<p>That way old v2 code would still work without any changes.