如何在ExpressJS中以条件状态渲染页面？

huangapple
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英文:

How can I render pages in conditional states in ExpressJS?

问题

以下是您提供的代码块的翻译部分：

  1. var express = require('express');
  3. var newsRouter = express.Router();
  5. newsRouter.get('/:news_param', (req, res) => {
  6.     let news_params = '/haberler/' + req.params.news_param;
  8.     req.news_list.forEach((news_obj) => {
  9.         if (news_params == news_obj.news_addr) res.render(req.params.news_param);
  10.     });
  11. });
  13. newsRouter.post('/', (req, res) => {
  14.     res.render('news', { news_fetch_from_database: news_list });
  15. })
  17. newsRouter.use((req, res) => {
  18.     res.render('404_page_news');
  19. });
  21. module.exports = newsRouter;

newsRouter.get('/:news_param', ...); 当我像这样添加 res.redirect('/404'); 并访问与404页面不同的任何页面时，会产生以下错误：

  1. ...
  3. newsRouter.get('/:news_param', (req, res) => {
  4.     let news_params = '/haberler/' + req.params.news_param;
  6.     req.news_list.forEach((news_obj) => {
  7.         if (news_params == news_obj.news_addr) res.render(req.params.news_param);
  8.     });
  10.     res.redirect('/404');
  11. ...
  12. });
  1. Error [ERR_HTTP_HEADERS_SENT]: 在响应头已发送给客户端后无法设置头
  2.     at new NodeError (node:internal/errors:387:5)
  3.     at ServerResponse.setHeader (node:_http_outgoing:644:11)
  4.     at ServerResponse.header (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:767:10)
  5.     at ServerResponse.location (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:884:15)
  6.     at ServerResponse.redirect (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:922:18)
  7.     at /home/alimkoca/Softwares/szal_web/news.js:12:9
  8.     at Layer.handle [as handle_request] (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/layer.js:95:5)
  9.     at next (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/route.js:137:13)
  10.     at Route.dispatch (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/route.js:112:3)
  11.     at Layer.handle [as handle_request] (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/layer.js:95:5)

我需要轻松处理 req.params 中的参数以便渲染页面，但我现在无法解决这个问题。并且出于安全问题，我不想使用文件系统API。

我只是运行了 npm start 命令并访问了任何有效的页面，然后像我上面表达的那样产生了以下错误：

  1. Error [ERR_HTTP_HEADERS_SENT]: 在响应头已发送给客户端后无法设置头
  2.     at new NodeError (node:internal/errors:387:5)
  3.     at ServerResponse.setHeader (node:_http_outgoing:644:11)
  4.     at ServerResponse.header (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:767:10)
  5.     at ServerResponse.location (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:884:15)
  6.     at ServerResponse.redirect (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:922:18)
  7.     at /home/alimkoca/Softwares/szal_web/news.js:12:9
  8.     at Layer.handle [as handle_request] (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/layer.js:95:5)
  9.     at next (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/route.js:137:13)
  10.     at Route.dispatch (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/route.js:112:3)
  11.     at Layer.handle [as handle_request] (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/layer.js:95:5)
英文:

I have the following code block:

  1. var express = require('express');
  3. var newsRouter = express.Router();
  5. newsRouter.get('/:news_param', (req, res) => {
  6.     let news_params = '/haberler/' + req.params.news_param;
  8.     req.news_list.forEach((news_obj) => {
  9.         if (news_params == news_obj.news_addr) res.render(req.params.news_param);
  10.     });
  11. });
  13. newsRouter.post('/', (req, res) => {
  14.     res.render('news', { news_fetch_from_database: news_list });
  15. })
  17. newsRouter.use((req, res) => {
  18.     res.render('404_page_news');
  19. });
  21. module.exports = newsRouter;

newsRouter.get('/:news_param', ...); gives the following error when I add res.redirect('/404'); like this and visit any page different than 404 page:

  1. ...
  3. newsRouter.get('/:news_param', (req, res) => {
  4.     let news_params = '/haberler/' + req.params.news_param;
  6.     req.news_list.forEach((news_obj) => {
  7.         if (news_params == news_obj.news_addr) res.render(req.params.news_param);
  8.     });
  10.     res.redirect('/404');
  11. ...
  12. });
  1. Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
  2.     at new NodeError (node:internal/errors:387:5)
  3.     at ServerResponse.setHeader (node:_http_outgoing:644:11)
  4.     at ServerResponse.header (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:767:10)
  5.     at ServerResponse.location (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:884:15)
  6.     at ServerResponse.redirect (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:922:18)
  7.     at /home/alimkoca/Softwares/szal_web/news.js:12:9
  8.     at Layer.handle [as handle_request] (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/layer.js:95:5)
  9.     at next (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/route.js:137:13)
  10.     at Route.dispatch (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/route.js:112:3)
  11.     at Layer.handle [as handle_request] (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/layer.js:95:5)

And I need to handle parameters in req.params for rendering pages easily, but I can't solve this issue right now. And I don't want to use filesystem API for security issues.

I simply ran the npm start command and visited any valid page, then it gave the following error as I expressed above:

  1. Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
  2.     at new NodeError (node:internal/errors:387:5)
  3.     at ServerResponse.setHeader (node:_http_outgoing:644:11)
  4.     at ServerResponse.header (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:767:10)
  5.     at ServerResponse.location (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:884:15)
  6.     at ServerResponse.redirect (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/response.js:922:18)
  7.     at /home/alimkoca/Softwares/szal_web/news.js:12:9
  8.     at Layer.handle [as handle_request] (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/layer.js:95:5)
  9.     at next (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/route.js:137:13)
  10.     at Route.dispatch (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/route.js:112:3)
  11.     at Layer.handle [as handle_request] (/home/alimkoca/Softwares/szal_web/node_modules/express/lib/router/layer.js:95:5)

答案1

得分: 1

The code is always, unconditionally performing this operation:

这段代码始终无条件执行此操作：

res.redirect('/404');

Which will fail with the error given if the code has already performed this operation:

如果代码已经执行了此操作，则会失败，并显示给定的错误：

res.render(req.params.news_param);

For exactly the reason implied by the error... You can't return a response after you've already returned a response.

这个错误的原因正如错误所暗示的那样...在已经返回响应之后，你不能再返回响应。

It sounds like you want to only conditionally return the 404 response. For example, if no matching record was found:

看起来你只想在某些条件下返回404响应。例如，如果没有找到匹配的记录：

let news_params = '/haberler/' + req.params.news_param;
let record_found = false;

req.news_list.forEach((news_obj) => {
if (news_params == news_obj.news_addr) {
res.render(req.params.news_param);
record_found = true;
}
});

if (!record_found) {
res.redirect('/404');
}

Or even just return from the function when the record is found:

或者当找到记录时，甚至可以从函数中返回：

let news_params = '/haberler/' + req.params.news_param;

for (let news_obj of req.news_list) {
if (news_params == news_obj.news_addr) {
res.render(req.params.news_param);
return;
}
}

res.redirect('/404');

英文:

The code is always, unconditionally performing this operation:

  1. res.redirect('/404');

Which will fail with the error given if the code has already performed this operation:

  1. res.render(req.params.news_param);

For exactly the reason implied by the error... You can't return a response after you've already returned a response.

It sounds like you want to only conditionally return the 404 response. For example, if no matching record was found:

  1. let news_params = '/haberler/' + req.params.news_param;
  2. let record_found = false;
  4. req.news_list.forEach((news_obj) => {
  5.   if (news_params == news_obj.news_addr) {
  6.     res.render(req.params.news_param);
  7.     record_found = true;
  8.   }
  9. });
  11. if (!record_found) {
  12.   res.redirect('/404');
  13. }

Or even just return from the function when the record is found:

  1. let news_params = '/haberler/' + req.params.news_param;
  3. for (let news_obj of req.news_list) {
  4.   if (news_params == news_obj.news_addr) {
  5.     res.render(req.params.news_param);
  6.     return;
  7.   }
  8. }
  10. res.redirect('/404');

huangapple
  • 本文由 发表于 2023年6月13日 00:55:29
  • 转载请务必保留本文链接：https://go.coder-hub.com/76458790.html
  • backend
  • express
  • javascript
  • node.js
  • web
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