Best method to include an external js with the current HTTP protocol

What's the cleanest method to include an external javascript using the current HTTP开发者_开发知识库 protocol type to avoid SSL partial security issues.

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<script src="//whatever-domain.com/path/to/script.js" type="text/javascript"></script>

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Dropping the scheme, but leaving the double slash will use the current scheme

//www.example.com/foo/bar.js