Microsoft made available to testers on June 18 of what's likely one of the last preview builds of its TypeScript language, compiler and tools.

TypeScript .9 is available for download from the TypeScript site. The latest update, which Microsoft officials described as the biggest TypeScript preview update to date, includes a bunch of new features in the language, compiler and associated tools.

The biggest new feature is the addition of generics, which allow developers to take advantage of better static error reporting and improved tooling "in many cases without any additional type annotations," officials said. The TypeScript compiler also has been re-engineered so it works better with large projects (in excess of 100,000 lines of code) in an interactive environment.

TypeScript, a Microsoft-developed superset of JavaScript, is available under an Apache 2.0 open-source license. Microsoft launched the first preview build of TypeScript in October 2012.

TypeScript was developed by a team of about 50 . Among the core team members are Microsoft Technical Fellow Anders Hejlsberg, the father of C# and TurboPascal; Microsoft Technical Fellow Steve Lucco; and Program Manager Luke Hoban, who has worked, in the past, on the JavaScript language and development experience. A new Channel 9 video featuring these three execs talking about what the team has learned since fielding the first preview of TypeScript is embedded below.

I asked Microsoft when we should expect the first "non-preview"/gold version of TypeScript. No word back so far, but I'd assume it will be in the coming few months, given the preview cadence.

Update: Microsoft officials are saying TypeScript 1.0 will ship "later this year."