You can't assign a value to false, for example, so "anything" isn't everything (Node v22.17.0).

    > false = 4
    false = 4
    ^^^^^
    
    Uncaught SyntaxError: Invalid left-hand side in assignment

Fascinatingly enough though, you can assign a value to NaN. It doesn't stick tho.

    > NaN
    NaN
    > NaN = 42
    42
    > NaN
    NaN
    >

(map behaves as described.)