Closure was also interesting because it integrated type checking and minification, which made minification significantly more useful.
With normal Javascript and typescript, you can't minify property names, so `foo.bar.doSomethingVeryComplicated()` can only be turned into `a.bar.doSomethingVeryComplicated()`, not `a.b.c()`, like with Closure. This is because objects can be indexed by strings. Something like `foo.bar[function]()` is perfectly valid JS, where the value of `function` might come from the user.
A minifier can't guarantee that such expressions won't be used, so it cannot optimize property accesses. Because Closure was a type checker and a minifier at the same time, it could minify the properties declared as private, while leaving the public ones intact.
With normal Javascript and typescript, you can't minify property names, so `foo.bar.doSomethingVeryComplicated()` can only be turned into `a.bar.doSomethingVeryComplicated()`, not `a.b.c()`, like with Closure. This is because objects can be indexed by strings. Something like `foo.bar[function]()` is perfectly valid JS, where the value of `function` might come from the user.
A minifier can't guarantee that such expressions won't be used, so it cannot optimize property accesses. Because Closure was a type checker and a minifier at the same time, it could minify the properties declared as private, while leaving the public ones intact.