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Muhammad Ali (Nerdjfpb)
Muhammad Ali (Nerdjfpb)

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Day 28 – Middlewares - Learning Node JS In 30 Days [Mini series]

Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. The next middleware function is commonly denoted by a variable named next. (official document)

Do you understand anything of it ?

In short, normally we use middleware to checking something. Like – if anyone is a authentic user or is the user is admin.

Middleware functions can perform the following tasks:

  • Execute any code.
  • Make changes to the request and the response objects.
  • End the request-response cycle.
  • Call the next middleware function in the stack.

An Express application can use the following types of middleware:

  • Application-level middleware
  • Router-level middleware
  • Error-handling middleware
  • Built-in middleware
  • Third-party middleware

You can check the more details –

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Let’s use a middleware

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we have 3 elements here – request, response and next cycle here. In the middleware we just console log the time. So when we’ll call the route, this function will be called always.

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See the result when we hit the url –

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You can see the graphical version here

Originally it published on nerdjfpbblog. You can connect with me in twitter or linkedin !

You can read the old posts from this series (below)

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