Express JS

Overview Middleware functions are functions that have access to the request object (req), the response object (res), and the next function in the application’s request-response cycle. The next function is a function in the Express router which, when invoked, executes the middleware succeeding the current middleware. Middleware functions can perform the following tasks: If the current middleware function does not end the request-response cycle,…

You can create chainable route handlers for a route path by using app.route(). Because the path is specified at a single location, creating modular routes is helpful, as is reducing redundancy and typos Here is an example of chained route handlers that are defined by using app.route(). express.Router Use the express.Router class to create modular, mountable route handlers. A Router instance…

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. Route handlers…

Route parameters are named URL segments that are used to capture the values specified at their position in the URL. The captured values are populated in the req.params object, with the name of the route parameter specified in the path as their respective keys. Route path: /users/:userId/books/:bookId Request URL: http://localhost:3000/users/34/books/8989 req.params: { “userId”: “34”, “bookId”: “8989” }…

Routing refers to how an application’s endpoints (URIs) respond to client requests. You define routing using methods of the Express app object that correspond to HTTP methods; for example, app.get() to handle GET requests and app.post to handle POST requests. These routing methods specify a callback function (sometimes called “handler functions”) called when the application receives a request to the specified route…