The background info:

Apple's proposal for HTML template defines the specifications, but still does not provide native mechanisms to instantiate it with javaScript values. The problem lies with incompatible template syntaxes between frameworks. This makes it hard for web developers to combine components they use from different libraries.

Some rules proposed

1. to create a component to create a shadow tree from HTML templates with out having to construct the DOM tree.
2. to create a contact card component for objects like email, it should make it easy to generate DOM tree likes.
3. to create a contact card as number 2. in addition to make edits to updates like email when corresponding to JS values.
4. to create a JS library to add support for capitalizing test read off javaScript objects before they get inserted.
5. any JS framework should be able to its own bidirectional binding mechanisms to propagate values back from shadow treet to contact card
6. create a search-field component to be able to show a checked box when users have already chosen to ignore case sensitivity in settings.
7. create a search-field component to be able to show fallback "keywords" when there are no custom placeholders.
8. a contact card should not show labels for an email address if the underlying JS object does not have specifications.
9. to create a contact list to be able to use a single template to instantiate an array of a contact-card components.

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Apple's Proposal

Apple has published their proposal address all these concerns when it comes to HTML templates elements in order to create a standard instance between all JS objects, libraries, and regarding the DOM:

https://github.com/w3c/webcomponents/blob/gh-pages/proposals/Template-Instantiation.md