Consider adding a module level visibility modifier.

Currently to protect integrity of data one can only use classes with private or protected fields. Classes are harder to work with compared to object literals. Being able to specify that certain fields are invisible to outside modules would be a valuable addition to support programming in functional style in TypeScript.

So what I am suggesting is to be able to specify whether a field of an interface is exported from a module or not. This also means that the instance of such interface can only be created within the module it is declared.

The similar features can be found in:

• F# called signature files: http://msdn.microsoft.com/en-us/library/dd233196.aspx
• Haskell called export lists: http://www.haskell.org/onlinereport/modules.html

首先檢視提議的模組層級可見性行為，以及所參照的 F# 簽章檔案和 Haskell 匯出清單。確定預期的介面語法、模組邊界，以及可以如何建立執行個體。當設計已獲得解決，且行為已充分規格化以供實作和測試時，即表示完成。