问题描述
我是Node的新手，所以如果我不明显，请原谅我.在node.js表达app.get函数的快速应用程序中，我们通常将route和view作为参数传递例如
I am newbie in node so please forgive me if i am not getting obvious.In node.js express application for app.get function we typically pass route and view as parameterse.g.
app.get('/users', user.list);
但是在 passport-google示例中，我发现它们是称为
but in passport-google example I found that they are calling it as
app.get('/users', ensureAuthenticated, user.list);
其中sureAuthenticated是一个函数
where ensureAuthenticated is a function
function ensureAuthenticated(req, res, next) {
if (req.isAuthenticated()) { return next(); }
res.redirect('/login')
}
简而言之，这意味着有多个在运行时被依次调用的回调.我尝试添加一些其他功能以使其看起来像
In short this means there are multiple callbacks which while running are called in series. i tried adding couple of more functions to make it look like
app.get('/users', ensureAuthenticated, dummy1, dummy2, user.list);
，我发现确保已连续调用Authenticated，dummy1，dummy2，user.list.
and i found ensureAuthenticated, dummy1, dummy2, user.list is getting called in series.
对于我的特定要求，我发现以上述形式顺序调用函数是一种非常优雅的解决方案，而不是使用异步序列.有人可以向我解释一下它是如何工作的，以及我一般如何实现类似的功能.
for my specific requirement i find calling functions sequentially in above form is quite elegant solution rather that using async series. can somebody explain me how it really works and how i can implement similar functionality in general.
推荐答案
在Express中，路径后的每个参数都按顺序调用.通常，这是一种实现中间件的方法(如您在提供的示例中所见).
In Express, each argument after the path is called in sequence. Usually, this is a way of implementing middleware (as you can see in the example you provided).
app.get('/users', middleware1, middleware2, middleware3, processRequest);
function middleware1(req, res, next){
// perform middleware function e.g. check if user is authenticated
next(); // move on to the next middleware
// or
next(err); // trigger error handler, usually to serve error page e.g. 403, 501 etc
}
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