javascript答案是它返回一个用第二组参数再次调用的函数。

The "javascript" answer is that it returns a function which is called again with those 2nd set of arguments.

该函数是链中每个策略失败的累加器。

That function is the "accumulator for failures from each strategy in the chain".

https://github.com/jaredhanson/passport/blob/master/lib/middleware /authenticate.js