{"id":1238,"date":"2025-05-14T13:25:42","date_gmt":"2025-05-14T13:25:42","guid":{"rendered":"https:\/\/www.wordpress-prod.sharpener.tech\/?p=1238"},"modified":"2025-05-14T13:25:43","modified_gmt":"2025-05-14T13:25:43","slug":"middleware-script","status":"publish","type":"post","link":"https:\/\/www.sharpener.tech\/blog\/middleware-script\/","title":{"rendered":"Addition to Library story and middleware working"},"content":{"rendered":"\n<figure class=\"wp-block-image size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/www.wordpress-prod.sharpener.tech\/wp-content\/uploads\/2025\/05\/Middleware-Script-1024x683.jpg\" alt=\"\" class=\"wp-image-1240\" srcset=\"https:\/\/sharpener-wordpress.s3.ap-south-1.amazonaws.com\/blog\/wp-content\/uploads\/2025\/05\/14132524\/Middleware-Script-1024x683.jpg 1024w, https:\/\/sharpener-wordpress.s3.ap-south-1.amazonaws.com\/blog\/wp-content\/uploads\/2025\/05\/14132524\/Middleware-Script-300x200.jpg 300w, https:\/\/sharpener-wordpress.s3.ap-south-1.amazonaws.com\/blog\/wp-content\/uploads\/2025\/05\/14132524\/Middleware-Script-768x512.jpg 768w, https:\/\/sharpener-wordpress.s3.ap-south-1.amazonaws.com\/blog\/wp-content\/uploads\/2025\/05\/14132524\/Middleware-Script.jpg 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Now that we are familiar with the concept of middleware let\u2019s try to deep dive into different kinds of middleware and their use cases.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Let me give you an instance of the libraries that i had back in my college.<br>Each library was special and had a unique<br>Imagine visiting <strong>three different libraries<\/strong>, each with a unique purpose and functionality.&nbsp;<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These libraries represent <strong>middleware<\/strong>, where each performs a specific task or handles a unique scenario, depending on its use case.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Library 1: Small Library: Basic Access<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>This library is in a quiet neighborhood with a small collection of books.<\/li>\n\n\n\n<li>The librarian at the entrance checks your membership card. If it\u2019s valid, you\u2019re allowed to borrow any book directly.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Use case:<\/strong><strong><br><\/strong>This library is like a <strong>basic authentication middleware<\/strong>, ensuring only valid members can access the system without adding unnecessary steps. It\u2019s simple and efficient.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Library 2: Big Library: Comprehensive Services<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>This library is large and serves many users.<\/li>\n\n\n\n<li>Your membership is verified at the entrance, and overdue books are checked.<\/li>\n\n\n\n<li>Inside, a digital system offers <strong>personalized book recommendations<\/strong> based on your past borrowing history.<\/li>\n\n\n\n<li>For special collections, you must request additional access through a separate process.<\/li>\n\n\n\n<li>Finally, you can borrow books at the checkout desk.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Use case:<\/strong><strong><br><\/strong>This library works like a middleware chain, where each step does something useful or checks a specific rule. It\u2019s designed for bigger systems that need more features and processes.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Research Library: Specialized Access<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>This library is for researchers and professionals.<\/li>\n\n\n\n<li>To enter, you must show proof of your profession, like a university ID or research credentials.<\/li>\n\n\n\n<li>Inside, the library provides access to <strong>specialized resources<\/strong>, such as rare books, journals, or databases, tailored for academic or professional use.<\/li>\n\n\n\n<li>There\u2019s also a team to help you retrieve hard-to-find resources or sign up for workshops.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Use case:<\/strong><strong><br><\/strong>This library acts like <strong>custom middleware<\/strong>, focusing on specialized users with specific needs, ensuring they get the right tools and data for their tasks.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><br>In this analogy, each library showcases how middleware can serve different purposes based on the requirements:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>The <strong>Small Library<\/strong> demonstrates <strong>basic middleware<\/strong>, performing essential tasks like authentication to ensure quick and simple access.<\/li>\n\n\n\n<li>The <strong>Big Library<\/strong> highlights a <strong>chain of middleware<\/strong>, where multiple layers work together to provide personalized services, additional checks, and enhanced user experiences.<\/li>\n\n\n\n<li>The <strong>Research Library<\/strong> represents <strong>custom middleware<\/strong>, designed for specific, advanced use cases to cater to unique audiences with tailored features.<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\"><br><br>If you\u2019re visiting both the <strong>Main Library<\/strong> and the <strong>Research Wing<\/strong> in your college library system, you experience the benefits of both sections seamlessly.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Combining Access and Privileges<\/strong><\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Main Library Visit:<\/strong>\n<ul class=\"wp-block-list\">\n<li>As you enter the <strong>Main Library<\/strong>, the system identifies you and checks your borrowing history.<\/li>\n\n\n\n<li>You are then provided with a list of personalized book recommendations tailored to your previous activity.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Transition to the Research Wing:<\/strong>\n<ul class=\"wp-block-list\">\n<li>When you proceed to the <strong>Research Wing<\/strong>, you show your research credentials.<\/li>\n\n\n\n<li>Along with access to the exclusive resources, such as rare books and journals, you also receive guidance from specialized staff to make the most of your visit.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">In this case, you benefit from all functionalities: personalized book recommendations from the <strong>Main Library<\/strong> and advanced privileges from the <strong>Research Wing<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">So in this case if let\u2019s say you are visiting the big and specilised library you will get an access to some recommnedatainos as well as some speciliassed privileges for being a part of research library so in the same way if the request passes through multiple middlewares it also get\u2019s some added functionalities.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><br><strong>Coding Example:<\/strong><br><br>We want to add specific functionalities to our req (request) object, such as book recommendations and access permissions. To achieve this, we&#8217;ll use middleware to modify the req object before it reaches the routes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><br><br>const express = require(&#8216;express&#8217;);<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">const app = express();<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\/\/ Middleware for Big Library<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">app.use(&#8216;\/big-library&#8217;, (req, res, next) =&gt; {<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">&nbsp;&nbsp;req.recommendations = [&#8216;The Hobbit&#8217;, &#8216;Harry Potter&#8217;]; \/\/ Adding recommendations<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">&nbsp;&nbsp;next();<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">});<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\/\/ Middleware for Research Library<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">app.use(&#8216;\/research-library&#8217;, (req, res, next) =&gt; {<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">&nbsp;&nbsp;req.access = &#8216;granted&#8217;; \/\/ Granting access<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">&nbsp;&nbsp;next();<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">});<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\/\/ Route for Big Library<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">app.get(&#8216;\/big-library&#8217;, (req, res) =&gt; {<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">&nbsp;&nbsp;res.send(`Big Library Recommendations: ${req.recommendations.join(&#8216;, &#8216;)}`);<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">});<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\/\/ Route for Research Library<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">app.get(&#8216;\/research-library&#8217;, (req, res) =&gt; {<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">&nbsp;&nbsp;res.send(`Research Library Access: ${req.access}`);<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">});<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\/\/ Start the server<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">app.listen(3000, () =&gt; console.log(&#8216;Server running on http:\/\/localhost:3000&#8217;));<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Key Features:<\/strong><\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Big Library Middleware<\/strong>: Adds a list of book recommendations.<\/li>\n\n\n\n<li><strong>Research Library Middleware<\/strong>: Grants access to special resources.<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>How It Works:<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>We use middleware to modify the req object by adding properties (req.recommendations and req.access) as the request travels through.<\/li>\n\n\n\n<li><strong>Middleware<\/strong>: <strong>Each middleware function runs before the final route handler, so by the time the request reaches the route, it has the necessary information attached to it.<\/strong><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Why Middleware Is Useful Here:<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Since the request passes through the middleware, the necessary data (like book recommendations or access flags) gets added to it before the final route handler processes the request.<br>This makes it easy to manage and organize logic, especially when there are multiple steps or checks before a final action (like fetching a list of books or granting access).<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u2014&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8211;<br><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\" \/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Middleware Analogy<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Similarly, when a request in a web application passes through multiple middlewares, each one adds specific functionalities or checks before the request reaches its final destination.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Initial Middleware:<\/strong>\n<ul class=\"wp-block-list\">\n<li>A middleware for the <strong>Main Library<\/strong> enriches the request with data such as req.recommendations\u2014a list of book recommendations based on the user&#8217;s preferences.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Next Middleware:<\/strong>\n<ul class=\"wp-block-list\">\n<li>A middleware for the <strong>Research Wing<\/strong> further adds req.access\u2014specialized privileges or access flags for advanced resources.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">When the request reaches the final route handler, it has accumulated all the necessary enhancements. The route can now use these properties to provide a more tailored response to the user.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Now that we are familiar with the concept of middleware let\u2019s try to deep dive into different kinds of middleware and their use cases. Let me give you an instance&hellip;<\/p>\n","protected":false},"author":6,"featured_media":1240,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[],"class_list":["post-1238","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tips"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.6 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>How to Create Middleware in Express.js | Custom Middleware Script Guide<\/title>\n<meta name=\"description\" content=\"Learn how to write custom middleware scripts in Express.js. 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