Suggestion: also provide String.prototype.dedent()

[atk]

Like this:

String.dedent(`
  Whatever
`)
// vs
`
  Whatever
`.dedent()

[bakkot]

See some previous discussion.

I think these ought to behave slightly differently, as they would serve different use cases: String.dedent as a template tag should be the thing you use whenever you have a literal string in source, and would enforce the constraint that the first line is empty and the last line is whitespace (and would remove them), whereas String.prototype.dedent should be used for strings acquired from elsewhere (e.g. read from a file), and would not have the constraint on the first/last lines (and would not remove them).

[Zamralik]

would not have the constraint on the first/last lines (and would not remove them).

Which is no issue as you can do text.dedent().trim() to have them removed.