Private Member Minification Design Proposal

**Problem:** For front end data binding frameworks such as Angular, Knockout, React, etc, making the choice to use typescript results in larger minified output files. **Proposal:** Add a tsconfig option "minifyPrivateMembers" (default false) **Details:** Since front end binding frameworks can have references to members in html, we cannot easily minify these members using existing tooling. For example, using google closure compiler would require using an externs file for all the public properties I want to keep. That would be awful to hand maintain. It'd be really nice if typescript could just minify anything marked private. Typescript wouldn't even have to minify anything else, uglify can do the rest. **Edit:** removed incorrect example. Minification of private members in the greeter example is 18% better than minification in javascript only. I also expect many classes would have **many** more private members than public members, so savings could be much greater than 18%. Actually with many custom knockout bindingHandlers almost every single member can be made private! ``` this["greeting"] var x = "gr" + "eeting"; var y = this[x]; ``` If typescript notices that a class is using string access with variable strings to its own members it **could** choose to not minify private members for that class. Alternatively if this feature just breaks code like that then I think that's okay as long as it's documented. It will already break external use of private members, and that's why the option defaults to false. Created from here: https://github.com/Microsoft/TypeScript/issues/8#issuecomment-303423733