Express.js is a back end web application framework for building RESTful APIs with Node.js. It provides features such as middleware, routing, template engines, and error handling.
Queries in Express JS are the key-value pairs that are appended to the URL after the question mark (?). They are used to send small amounts of information to the server, such as parameters for filtering results or querying a database. Express JS automatically parses the query strings and stores them in the req.query object, which we can access in our route handlers.
Try catch is a way of handling errors in JavaScript. It allows us to execute some code and catch any errors that may occur, without stopping the program. In Express JS, try catch can be useful for catching errors in asynchronous code. By using try catch, we can send a proper response to the client, or pass the error to a global error handler.
Some of the features of Express JS are:
- Routing: It allows us to define application routes using HTTP methods and URLs, and handle different requests with different callback functions.
- Middleware: It enables us to execute additional functions between the request and the response, such as logging, authentication, error handling, etc.
- Template engines: It supports various template engines, such as EJS, Pug, Handlebars, etc., that allow us to render dynamic HTML pages with data from the server.
- Error handling: It provides a built-in error handler and a way to define custom error handlers for different types of errors.
- Security: It helps us to secure our web applications by providing features such as HTTPS support, CSRF protection, helmet middleware, etc.
- Ease of use: It is easy to install, set up, and customize, and it has a large and active community that provides documentation, tutorials, and support.
- Routing: It allows us to define application routes using HTTP methods and URLs, and handle different requests with different callback functions.
- Middleware: It enables us to execute additional functions between the request and the response, such as logging, authentication, error handling, etc.
- Template engines: It supports various template engines, such as EJS, Pug, Handlebars, etc., that allow us to render dynamic HTML pages with data from the server.
- Error handling: It provides a built-in error handler and a way to define custom error handlers for different types of errors.
- Security: It helps us to secure our web applications by providing features such as HTTPS support, CSRF protection, helmet middleware, etc.
- Ease of use: It is easy to install, set up, and customize, and it has a large and active community that provides documentation, tutorials, and support.
Some of the reasons why we use Express JS are:
- It is fast and easy to set up and customize.
- It supports RESTful APIs, which are a standard way of communicating data between web services.
- It has a large and active community that provides support and resources.
- It is compatible with many other Node.js modules and frameworks, such as MongoDB, Angular, React, etc.
- It is fast and easy to set up and customize.
- It supports RESTful APIs, which are a standard way of communicating data between web services.
- It has a large and active community that provides support and resources.
- It is compatible with many other Node.js modules and frameworks, such as MongoDB, Angular, React, etc.
Node.js is the runtime environment that allows us to run JavaScript on the server side, while Express.js is a framework built on top of Node.js to simplify the process of building web applications and APIs. Express.js is not mandatory when using Node.js, but it is a popular choice due to its simplicity and efficiency in handling web-related tasks.
Middleware in Express.js are functions that are executed in the middle of the request-response cycle. They can access and modify the request and response objects, perform some processing, and call the next middleware function in the chain. Middleware functions can be used for various purposes, such as logging, authentication, error handling, or performance optimization.
CORS stands for Cross-Origin Resource Sharing, which is a mechanism that allows web browsers to request resources from different origins such as different domains, protocols, or ports. CORS is useful for enabling web applications to access data from external APIs or services.
Some of the most common ones are:
- GET: This request is used to retrieve data from a web server.
- POST: This request is used to send data to a web server.
- PUT: This request is used to update or replace data on a web server.
- PATCH: This request is similar to PUT, but it only updates or modifies a part of the data on a web server.
- DELETE: This request is used to delete data from a web server.
- GET: This request is used to retrieve data from a web server.
- POST: This request is used to send data to a web server.
- PUT: This request is used to update or replace data on a web server.
- PATCH: This request is similar to PUT, but it only updates or modifies a part of the data on a web server.
- DELETE: This request is used to delete data from a web server.
The app.use function in Express JS is a way to add middleware functions to our application. It's crucial for setting up middleware and defining how our Express application should handle various aspects of the request-response cycle.