Deprecation: unless tag - marko-js/marko GitHub Wiki

The <unless> tag is deprecated in favor of inverting the expression inside the <if> tag.

<unless(x)>
 x is falsy!
</unless>

…becomes <if> with the unary negation operator (!):

<if(!x)>
 x is falsy!
</if>

To automatically fix deprecated marko syntax, try the marko migrate command from the CLI.