process.mainModule

blake

require.main 的备选方法。不同点，如果主模块在运行时改变，require.main可能会继续返回老的模块。可以认为，这两者引用了同一个模块。

Alternate way to retrieverequire.main.The difference is that if the main module changes at runtime, require.mainmight still refer to the original main module in modules that were requiredbefore the change occurred. Generally it's safe to assume that the two referto the same module.

和 require.main 一样, 如果没有入口脚本，将会返回undefined 。