JavaScript is a single-threaded programming language. This means that JavaScript can do only one thing at a single point in time. The JavaScript engine executes a script from the top of the file and works its way down. It creates the execution contexts, pushes, and pops functions onto and off the call stack in the execution phase.
The event loop in Node.js is a mechanism that allows the execution of JavaScript code in a non-blocking way, by using an event-driven, asynchronous programming model. The event loop is a single thread that runs in the background and handles all the tasks that are scheduled by the JavaScript runtime, such as I/O operations, timers, and promises.
The event loop operates in a continuous loop, where it repeatedly checks the message queue, also known as the task queue, for new tasks to execute. When a task is added to the queue, the event loop will start processing it. Once a task is completed, the event loop will check for any new tasks in the queue, and continue to process them in the order they were received.
Node.js uses a technique called "non-blocking I/O" which means that when a task, such as a database query or an HTTP request, is initiated, the event loop does not wait for the task to complete before moving on to the next task. Instead, it will register a callback function that will be executed once the task is completed, and continue to process other tasks in the meantime.
The event loop is what allows Node.js to handle a large number of concurrent connections without blocking the execution of the JavaScript code, making it well suited for building high-performance, scalable network applications.
Each file in a Node.js application is considered a module, and it has its own scope, which means that variables and functions defined inside a module are not accessible from outside of it, unless they are explicitly exported.
There are several ways to handle errors in Node.js, but the most common approach is to use the try...catch statement. Another way to handle errors in Node.js is to use the callback pattern, where we pass a callback function as an argument to a function that might throw an error
In synchronous code, the program execution blocks until a task is completed before moving on to the next task. On the other hand, asynchronous code allows the program to continue its execution while a task is being completed in the background. Asynchronous programming is particularly useful in Node.js because of its single-threaded nature. Using asynchronous code allows Node.js to handle a large number of concurrent connections without blocking the execution of the JavaScript code, making it well suited for building high-performance, scalable network applications.
A common use case for streams is reading large files, where instead of loading the entire file into memory, you can read the file in chunks using a readable stream, process each chunk, and write the result to another file using a writable stream. This approach allows you to handle large files without consuming too much memory.
Jest for Unit testing, Cypress for E2E
Build: Compile the application and its dependencies, and create a production-ready version of the code. This step may involve transpiling the code, minifying assets, and optimizing performance.
Package: Create a deployable package of the application, including all the necessary files and dependencies. This step may involve creating a Docker container, a tarball or a zip archive of the code.
Configure: Update the application's configuration for production, such as setting environment variables, modifying the logging level, and disabling debugging features.
Deploy: Copy the application package to the target environment, and configure the target environment to run the application. This step may involve installing dependencies, configuring a web server or a container orchestration platform, and starting the application.
Monitor: Monitor the application's performance, and troubleshoot any issues that may arise. This step may involve using monitoring tools, such as Prometheus, and log management services like ELK.
In Node.js, you can use the ws library to handle WebSockets. Here's an example of how you can use the ws library to create a simple WebSocket server:
const WebSocket = require('ws');
const server = new WebSocket.Server({ port: 8080 });
server.on('connection', (ws) => {
ws.on('message', (message) => {
console.log(`Received message: ${message}`);
ws.send(`Echo: ${message}`);
});
});