@matthewheck this would prevent Helmet from being able to handle value-less attributes. For example:

<Helmet
    script={[
        {"async": undefined}
    ]}
/>

It would also prevent you from removing an un-needed attribute on render. For example, if you wanted to remove the className or data attribute of a particular style element for identification purposes.

@matthewheck Thanks for your patience on this issue. We appreciate the PR. But @doctyper is correct, we still want to allow for undefined/null values for attributes for specific cases like the one he quotes above.

Your original issue #162 refers to the toLowerCase function throwing and that seems to be the real error case we need to check for. We should still allow the tag to be rendered though. The real trick is how we will check for duplicates of async: undefined, which I don't think the current code supports.

If you'd like to update, let me know. And thanks again for your patience.

@matthewheck ah, on second look, this is a valid solution. Thanks for the detailed consideration.

@doctyper This only affects primary keys (i.e. "name",
"charset", "http-equiv", "rel", "href", "property", "src", "innerHTML", "cssText") that have undefined/null values. async is not a primary key, and with this PR will still render as a valueless attribute. But note, with your particular example, it wouldn't render regardless of this PR because there is no primary key specified.

@cwelch5 - Apologies for not following up on the initial comments from you and @doctyper, but I'm glad this could be used!