What if the "shifted" string has a tie for the most common character?

It would be even better with highload tests :D

Funny kata! I enjoyed it

desription is short dence and also nice to reed.
I wish my companys documentation is written that way...

Description should be language-agnostic

Pretty much a duplicate of this kata.

Well, you're not afraid to invalidate existing solutions! :D ( Rightly - that's what Beta is for. )

Fixed.

You goddamn right! Now you get only letter, not object! Thank you!

letter is encoded as {'l': 3}. But it is a tuple. In JS, the appropriate encoding for that is as an array, not as an object ( witness all the hoops solvers are jumping through to get at the contents ).

Use appropriate datatypes!

( Unimportant: the second value is never used. So why pass it? )

Yup :]

Thank you for feedback! Fixed, as per your advice.

Initial code has return new String();. I applaud this effort! More kata should give datatypes for their inputs and outputs.

But it should be return "";, because JS distinguishes Objects ( that String ) and primitive values. And the return value should be a primitive string, not an Object.

Description changed, and this part removed from Pre-loaded.

Huh, right. My mistake. Came up with a bicycle. Thank you.

P.S. ASCII object preloaded - ASCIIObject: ASCIIObject['l'] => 108

Do you not know about String.prototype.charCodeAt, or why is this here?