I remember when the whole Ajax thing kicked in and JavaScript developers looked at Gmail, Gmaps, and the like and thought “I wonder what powers that?”

Well, the power comes from Closure a library and set of tools that the great JS hackers built over time as they created the applications at scale.

As soon as I joined Google I wanted to check out this code, and talked to a bunch of folks who were interested in open sourcing it. Well, these things take time, but now we are fortunate enough to have everything out there (interestingly, a lot of the code was open due to it being used in Google Doc).

What are the pieces?

The Closure Compiler compiles JavaScript into

compact, high-performance code. The compiler removes dead code and

rewrites and minimizes what’s left so that it downloads and runs

quickly. It also also checks syntax, variable references, and

types, and warns about common JavaScript pitfalls. These checks and

optimizations help you write apps that are less buggy and easier to

maintain. You can use the compiler with Closure Inspector,