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Extra - What is res, req? next? (node.js + express)

Chesed Kim 2021. 2. 19. 21:38
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res and req are objects? next is parameter??? Are they functions?

 

These are middleware function. [res, req] are definitely middleware function.

 

next is function - work somewhat like callback + middleware function.

 

From documentation:

You can provide multiple callback functions that behave like middleware to handle a request. The only exception is that these callbacks might invoke next('route') to bypass the remaining route callbacks. You can use this mechanism to impose pre-conditions on a route, then pass control to subsequent routes if there’s no reason to proceed with the current route.

 

Here is the clear Answer I found!

expressjs.com/ko/guide/writing-middleware.html

 

Express 앱에서 사용하기 위한 미들웨어 작성

Express 앱에서 사용하기 위한 미들웨어 작성 개요 미들웨어 함수는 요청 오브젝트(req), 응답 오브젝트 (res), 그리고 애플리케이션의 요청-응답 주기 중 그 다음의 미들웨어 함수 대한 액세스 권한

expressjs.com

For more exmaple, here monkelite.com/what-are-res-and-req-objects-in-node-js-express-framework/

 

What are res and req objects in Node.js Express framework -

In this article, we'll learn request and response objects in node and understand How to use them. What information and capabilities do they provide.

monkelite.com

stackoverflow.com/questions/39220957/nodejs-next-function-why

 

Nodejs next function, why?

I am developing apis with nodejs. I have seen there is a parameter passed in the function with req, res like this: bookRouter.use('/:bookId', function(req,res,next){ Book.findById(req.par...

stackoverflow.com

 

Btw, what is Express framework? Here!

www.tutorialspoint.com/nodejs/nodejs_express_framework.htm

 

Node.js - Express Framework - Tutorialspoint

Node.js - Express Framework Express Overview Express is a minimal and flexible Node.js web application framework that provides a robust set of features to develop web and mobile applications. It facilitates the rapid development of Node based Web applicati

www.tutorialspoint.com

 

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