Hacker News Reader

Or a Greek capital letter Lambda: Λ

Λ(['1', '2', '3'])

Is that a valid variable name? Would that mean Λ is unicode?

It is a valid Unicode letter so should be acceptable in EcmaScript 5.

How does one type that?

Like this: Λ ;)

Windows: Alt+x 03BB

Linux: Ctrl+Shift+u 03BB (still pressing Ctrl+Shift)