req.locals vs. res.locals vs. res.data vs. req.data vs. Express中间件中的app.locals [英] req.locals vs. res.locals vs. res.data vs. req.data vs. app.locals in Express middleware

问题描述

有一些类似的问题，但我的问题是，如果我想传播中间结果，我沿着不同的路由中间件，最好的方法是什么？

  app.use（f1）; app.use（F2）; app.use（F3）; 
 
函数f1（req，res，next）{
 //一些数据库查询被执行，我得到结果，说x1 
 res.locals.dbResults = {... }; 
 next（）; 
} 
 
函数f2（req，res，next）{
 //更多根据req.locals.dbResults处理
 res.locals.moreResults = {。 ...}; 
 next（）; 
  

}
...

我认为通过使用 req .locals可以通过不同的中间件获得相同的数据传播。此外，似乎请求和响应对象都在请求开始时将本地属性初始化为空对象。

另外，可以设置res.mydata或者req.mydata属性？

在理论上，app.locals也可以用于传递这些数据，通过不同的中间件，因为它将持续跨越中间件，但是与常规使用app.local相反。它更多地用于应用程序特定的数据。还有必要在请求 - 响应周期结束时清除数据，因此相同的变量可以用于下一个请求。

什么是通过中间件传播中间结果的最佳和标准方式？

解决方案

正如您所提到的， req.locals ， res.locals 甚至你自己定义的键 res.userData 可以使用。除了命名，没有什么不同。话虽如此，但是我建议使用 res.locals ，因为这是在官方的Express.js文档中提到的唯一一个： p>

res.locals
包含响应局部变量作用于请求的对象，因此仅可用在该请求/响应周期（如果有的话）中呈现
的视图。否则，此
属性与 app.locals 相同。

此属性对于显示请求很有用级别信息如
请求路径名称，认证用户，用户设置等。

资料来源： http://expressjs.com/en/api.html#res.locals

由于正式记录，所以使用 res.locals 属性的机会更少（向后兼容）。如果您选择自己的密钥，Express.js的将来版本总是有机会覆盖您的数据，因为它们恰好使用相同的密钥。使用 res.locals 时不会发生这种情况。这也使新人更容易理解您的代码，因为大多数项目使用 res.locals 来存储中间件数据。

There are some similar questions asked but my question is that if I want to propagate intermediate results that I get along the different routing middleware, what is the best way to do that?

app.use(f1); app.use(f2); app.use(f3);

function f1(req,res,next) {
  //some database queries are executed and I get results, say x1
  res.locals.dbResults = {...};
  next();
}

function f2(req,res,next) {
 //more processing based upon req.locals.dbResults 
 res.locals.moreResults = {....};
 next();

} ...

I think that I can get the same propagation of data through the different middleware by using req.locals. Also, it appears that the request and response objects both have the locals properties initialized to an empty object at the start of the request.

Also, one can set res.mydata or req.mydata properties too?

In theory, app.locals can also be used for passing this data along through the different middleware as it will persist across middlewares but that would be contrary to the conventional use of app.locals. It is used more for application specific data. It will also be necessary to clear that data at the end of the request-response cycle so the same variables can be used for the next request.

What is the optimal and standard way to propagate intermediate results through middleware?

解决方案

As you mentioned, both req.locals, res.locals or even your own defined key res.userData can be used. Apart from naming, there's no real difference. That being said, I would however recommend to use res.locals as this is the only one mentioned in the official Express.js documentation:

res.locals An object that contains response local variables scoped to the request, and therefore available only to the view(s) rendered during that request / response cycle (if any). Otherwise, this property is identical to app.locals.

This property is useful for exposing request-level information such as the request path name, authenticated user, user settings, and so on.

Source: http://expressjs.com/en/api.html#res.locals

Because it's officially documented, there's less chance of the res.locals property ever being used for anything else (backwards compatibility). If you pick out your own key, there's always a chance future versions of Express.js will overwrite your data because they happen to use the same key. This won't happen when using res.locals. It also makes it easier for new people to understand your code as most projects use res.locals to store middleware data.

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