Is the docker daemon running?. Can't operate learn python mongoose connect learncbse ascii art align vertical center text div color gradient in flutter checkbox in flutter electromagnetic spectrum metasploit metafrash vim download myspace tailwind flex align items center movie app movies bootstrap button group pacman 30th anniversary pacman install numpy pip numpy no module named 'numpy' python pip install numpy Import "numpy" could not be resolved django python install numpy stripe test card flutter text field form flutter text field flutter input text in container GridView in flutter pm2 starts npm run start pm2 start npm start pm2 start with name authentication vs authorization purple hex code Support for password authentication was removed on August 13, Please use a personal access token instead.
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Check the spelling of the name, or if a path was included, verify that the path is correct and try again. Unable to correct problems, you have held broken packages. Unexpected end of JSON input while parsing near ' There is likely additional logging output above lite server this operation is rejected by user system npm jquery in react npm ERR!
Another active Homebrew update process is already in progress flutter outline button Notifications for installing dependencies from package. It should create new npm-shrinkwrap. Express provides a thin layer on top of Node. Express is a minimal, un-opinionated framework.
For fans of simplicity, this is a big plus among all other frameworks because you can build your application with your own preference and no unnecessary learning curve. Even though the framework is un-opinionated, it does have the generator that generates specific project folder structure. After installing express-generator npm package and creating application skeleton with generator command, an application folder with clear hierarchy will be created to help you organize images, front-end static JavaScript, stylesheet files and HTML template files.
Middleware are basically just functions that have full access to both request and response objects. An Express application is essentially Node. Template engines allow developer to embed backend variables into HTML files, and when requested the template file will be rendered to plain HTML format with the variables interpolated with their actual values.
By default, the express-generator uses Pug originally known as Jade template engine, but other options like Mustache and EJS also work with Express seamlessly. As a minimal framework, Express does not consider database integration as a required aspect within its package, thus it leans toward no specific database usage whatsoever. These third party database drivers do not conform to unified syntax when doing CRUD instructions, which makes switching databases a big hassle and error prone.
Improper maintenance of an application can result in issues related to stability or flexibility, often leading to the app's failure. If the code is not well-written or if developers use outdated tools, the performance can suffer, and users might experience more bugs and app crashes.
In the worst case scenario, it might become impossible to introduce new features without rewriting the codebase from scratch. This essentially means that applications can talk to a server in the background of the application. It uses some core components to function:. Unlike the other programming languages, Node.
It is required for those web applications where traffic rate is very high. It is being used by the famous websites like Linked in, Twitter and Gmail. The runtime environment of Node. Due to this reason, even the developers find it easy going which keeps them happy and relaxed. It is pertinent for real-time collaborative apps. Whenever data is needed nodejs registers a callback and sends the operation to this event loop.
Whenever the data is available the callback is called. ES introduced Asynchronous functions. Async functions are essentially a cleaner way to work with asynchronous code in JavaScript. Async functions can make use of the await expression. This will pause the async function and wait for the Promise to resolve prior to moving on.
LTS versions of Node. Changes to LTS versions are limited to bug fixes for stability, security updates, possible npm updates, documentation updates and certain performance improvements that can be demonstrated to not break existing applications.
Keeping the API declaration separated from the network related configuration port, protocol, etc allows testing the API in-process, without performing network calls, with all the benefits that it brings to the table: fast testing execution and getting coverage metrics of the code.
It also allows deploying the same API under flexible and different network conditions. Bonus: better separation of concerns and cleaner code. The difference between process. Callback : A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action. Events : Every action on a computer is an event. Event module includes EventEmitter class which can be used to raise and handle custom events.
It is an architectural style as well as an approach for communications purposes that is often used in various web services development.
A query string is a part of a URL that assigns values to specified parameters. A query is the last part of URL. A cookie is a piece of data that is sent to the client-side with a request and is stored on the client-side itself by the Web Browser the user is currently using. The cookie-parser middleware's cookieParser function takes a secret string or array of strings as the first argument and an options object as the second argument.
Nodemon is a utility that will monitor for any changes in source and automatically restart your server. P rocess M anager 2 pm2 is a production process manager for Node. It allows to keep applications alive forever, to reload them without downtime and to facilitate common system admin tasks. The serve-favicon module lets us exclude requests for the favicon in our logger middleware. It also caches the icon in memory to improve performance by reducing disk access.
In addition, it provides an ETag based on the contents of the icon, rather than file system properties. C ross- O rigin R esource S haring CORS headers allow apps running in the browser to make requests to servers on different domains also known as origins.
CORS defines a way in which a browser and server can interact and determine whether or not it is safe to allow a cross-origin request. When a NodeJs application runs, it injects a global variable called process. The dotenv loads environment variables stored in the. Such as recursive mkdir , copy , and remove. A JavaScript date library for parsing, validating, manipulating, and formatting dates.
Routing defines the way in which the client requests are handled by the application endpoints. We define routing using methods of the Express app object that correspond to HTTP methods; for example, app. These routing methods "listens" for requests that match the specified route s and method s , and when it detects a match, it calls the specified callback function.
Route paths, in combination with a request method, define the endpoints at which requests can be made. Route paths can be strings, string patterns, or regular expressions. The characters? The hyphen - and the dot. The captured values are populated in the req. Blocking is when the execution of additional JavaScript in the Node. This happens because the event loop is unable to continue running JavaScript while a blocking operation is occurring. Synchronous methods in the Node. Native modules may also have blocking methods.
Blocking methods execute synchronously and non-blocking methods execute asynchronously. A promise is used to handle the asynchronous result of an operation. JavaScript is designed to not wait for an asynchronous block of code to completely execute before other synchronous parts of the code can run. With Promises, we can defer the execution of a code block until an async request is completed. This way, other operations can keep running without interruption. Await is basically syntactic sugar for Promises.
Putting the keyword async before a function tells the function to return a Promise. If the code returns something that is not a Promise , then JavaScript automatically wraps it into a resolved promise with that value. The await keyword simply makes JavaScript wait until that Promise settles and then returns its result. This information can be verified and trusted because it is digitally signed.
The jwt. It creates a unique string of characters representing the payload. In our case, the payload is an object containing only the id of the user. Microservices are a style of service-oriented architecture SOA where the app is structured on an assembly of interconnected services.
With microservices, the application architecture is built with lightweight protocols. The services are finely seeded in the architecture. Microservices disintegrate the app into smaller services and enable improved modularity. There are few things worth emphasizing about the superiority of microservices, and distributed systems generally, over monolithic architecture:. The next step is to define the routes for the microservices and then assign each to a target in the controller.
We have two endpoints. One endpoint called "about" that returns information about the application. And a "distance" endpoint that includes two path parameters, both Zip Codes of the Lego store. This endpoint returns the distance, in miles, between these two Zip Codes. Within the controller file, we are going to create a controller object with two properties.
Those properties are the functions to handle the requests we defined in the routes module. A promise is an object that represents the return value or the thrown exception that the function may eventually provide.
A promise can also be used as a proxy for a remote object to overcome latency. Promise is relatively an easy implementation for asynchronous operation.
The promise object returned from the function represents an operation which is not completed yet, but it guarantees to the caller of the operation that the operation will be completed in future. On the first pass, promises can mitigate the Pyramid of Doom : the situation where code marches to the right faster than it marches forward. Memcached is a general-purpose distributed memory caching system. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an external data source such as a database or API must be read.
Memcached is free and open-source software, licensed under the Revised BSD licence. We can store data to memcached server in key pair format. This increases the performance of the application.
The constructor of the memcached client take 2 different arguments server locations and options. The checksum aka hash sum calculation is a one-way process of mapping an extensive data set of variable length e. The length depends on a hashing algorithm. For the checksum generation, we can use node crypto module. The module uses createHash algorithm to create a checksum hash generator. The algorithm is dependent on the available algorithms supported by the version of OpenSSL on the platform.
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View code. What is Node. What are the benefits of using Node. What are the data types in Node. How to create a simple server in Node. Explain the concept of URL module in Node. How to execute an external program from within Node. What does the runtime environment mean in Node.
How do Node. What is the difference between Node. What are the core modules of Node. What is callback function in Node. How assert works in Node. What is an error-first callback? What is callback hell in Node. What are Promises in Node. What tools can be used to assure consistent style? When should you npm and when yarn? What is a stub? What is a test pyramid? How can you make sure your dependencies are safe? What is Event loop in Node. How does it work? If Node. What is REPL? What purpose it is used for?
What is asynchronous programming in Node. What is the difference between Asynchronous and Non-blocking? How to debug an application in Node. What are some of the most popular packages of Node. What is EventEmitter in Node. How many types of streams are present in node. What is crypto in Node. How do you cipher the secure information in Node. What is the use of DNS module in Node.
What are the security mechanisms available in Node. Name the types of API functions in Node. How does Node. What is the preferred method of resolving unhandled exceptions in Node. What is typically the first argument passed to a Node. How Node. What is JIT and how is it related to Node. What is chrome v8 engine? What is the purpose of using hidden classes in V8? How V8 compiles JavaScript code? What is V8 Templates? What is difference between put and patch?
List types of Http requests supported by Node. Why to use Express. Write the steps for setting up an Express JS application? Since node is a single threaded process, how to make use of all CPUs? What does emitter do and what is dispatcher? How to kill child processes that spawn their own child processes in Node. What do you understand by Reactor Pattern in Node. What are the key features of Node. What are globals in Node. What is chaining process in Node. What is a control flow function?
What are the steps does it execute? What is npm in Node. When to use Node. Explain how does Node. Is Node. How to make post request in Node. Can you create http server in Node. How to load html in Node.
How can you listen on port 80 with Node? What is the difference between operational and programmer errors? Why npm shrinkwrap is useful? What is your favourite HTTP framework and why?
What are the Challenges with Node. What are async functions in Node? Mention the steps by which you can async in Node. What are the timing features of Node. What is LTS releases of Node. Why should you separate Express 'app' and 'server'? What is the difference between process. What is difference between JavaScript and Node. What are the difference between Events and Callbacks?
What is the difference between req. How to handle file upload in Node. Explain the terms body-parser, cookie-parser, morgan, nodemon, pm2, serve-favicon, cors, dotenv, fs-extra, moment in Express JS? How does routing work in Node. How node. What is difference between promises and async-await in Node. How to build a microservices architecture with Node. How to use Q promise in Node.
How to implement Memcached in Node. How to generate and verify checksum of the given string in Nodejs Q. Is it possible to use "Class" in Node. Explain Error Handling approaches in Node. How would you handle errors for async code in Node. What are the use cases for the Node. Explain the concept of Domain in Node. Why Node. How to use locale i18n in Node. What are the types of memory leaks in node.
How to implement a Sleep function? How does the cluster load balance work in node. What is daemon process? How to synchronize data between multiple clients on node. How do you convert an existing callback API to promises?
How would you scale Node application? How to solve "Process out of Memory Exception" in Node. How does the cluster module work?
What is the difference between it and a load balancer? No Questions Write the steps for setting up an Express JS application. How to handle file upload in Node js? Explain the terms body-parser, cookie-parser, debug, jade, morgan, nodemon, pm2, serve-favicon, cors in Express JS? How Node prevents blocking code? What is difference between promise and async await in node js?
How to build a microservices architecture with node js? How to use Q promise in node js? How to use locale i18n in node js? How to Implement Memcached in Nodejs? Explain Error Handling approaches in Nodejs? How to generate and verify checksum of the given string in Nodejs What is Callback function in node. What is asynchronous programming in node. EventEmitter ;. Listner1 will not listen now. API ; app. PORT '' ; app. About Frequently Asked Node. Releases No releases published.
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