Express中app.locals和res.locals

待我称王封你为后i 2022-10-02 05:51 155阅读 0赞

**1.app.locals**

The app.locals object has properties that are local variables within the application.

app.locals.title
    // => 'My App'
    
    app.locals.email
    // => 'me@myapp.com'

Once set, the value of app.locals properties persist throughout the life of the application, in contrast with res.locals properties that are valid only for the lifetime of the request.

You can access local variables in templates rendered within the application. This is useful for providing helper functions to templates, as well as application-level data. Local variables are available in middleware via req.app.locals (see req.app)

app.locals.title = 'My App';
    app.locals.strftime = require('strftime');
    app.locals.email = 'me@myapp.com';

**2.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.

app.use(function(req, res, next){
      res.locals.user = req.user;
      res.locals.authenticated = ! req.user.anonymous;
      next();
    });

上面是官方文档解释，大致意思就是，locals可能存在于app对象中即：app.locals；也可能存在于res对象中，即：res.locals。两者都会将该对象传递至所渲染的页面中。不同的是，app.locals会在整个生命周期中起作用；而res.locals只会有当前请求中起作用。

参考文章：  
[http://www.expressjs.com.cn/4x/api.html\#app.locals][http_www.expressjs.com.cn_4x_api.html_app.locals]  
[https://itbilu.com/nodejs/npm/Ny0k0TKP-.html][https_itbilu.com_nodejs_npm_Ny0k0TKP-.html]  
[https://blog.csdn.net/Elliott\_Yoho/article/details/53537437][https_blog.csdn.net_Elliott_Yoho_article_details_53537437]  
[https://www.cnblogs.com/xxcanghai/p/6422640.html][https_www.cnblogs.com_xxcanghai_p_6422640.html]  
[https://www.jianshu.com/p/e8ecddba90e0][https_www.jianshu.com_p_e8ecddba90e0]  
[https://blog.csdn.net/kuangruike/article/details/52620941][https_blog.csdn.net_kuangruike_article_details_52620941]  
[https://blog.csdn.net/turne/article/details/67644288][https_blog.csdn.net_turne_article_details_67644288]

[http_www.expressjs.com.cn_4x_api.html_app.locals]: http://www.expressjs.com.cn/4x/api.html#app.locals
[https_itbilu.com_nodejs_npm_Ny0k0TKP-.html]: https://itbilu.com/nodejs/npm/Ny0k0TKP-.html
[https_blog.csdn.net_Elliott_Yoho_article_details_53537437]: https://blog.csdn.net/Elliott_Yoho/article/details/53537437
[https_www.cnblogs.com_xxcanghai_p_6422640.html]: https://www.cnblogs.com/xxcanghai/p/6422640.html
[https_www.jianshu.com_p_e8ecddba90e0]: https://www.jianshu.com/p/e8ecddba90e0
[https_blog.csdn.net_kuangruike_article_details_52620941]: https://blog.csdn.net/kuangruike/article/details/52620941
[https_blog.csdn.net_turne_article_details_67644288]: https://blog.csdn.net/turne/article/details/67644288