Microsoft/TypeScript — pull request #284 by DanielRosenwasser (2014-07-28 23:08:45+00:00)
Title: Disallow Trailing Commas in Object Literals Entirely for ES3 Targets

The idea is that since the ECMAScript 3 spec does not permit trailing commas in an object literal, we should not permit the construct unless we have a revised grammar for TypeScript that says otherwise.

This is a breaking change. I would personally rather amend the specification.

This is an extension of the work on #273.