Node js interview questions and answer part -2
Question :
What is the difference between tilde ~ and caret ^?
Answer:
In JavaScript package management, specifically with npm and package.json files, the tilde (~) and caret (^) symbols are used to specify version ranges for dependencies. Here’s the difference between the two:
- Tilde (~): The tilde (~) symbol specifies a version range that allows for patch-level updates. When used in the package.json file, it means that you accept any new patch-level releases, while keeping the major and minor versions fixed.
For example, if you specify a dependency as "package": "~1.2.3", it means you will accept any version that is greater than or equal to 1.2.3 but less than the next major release (e.g., 1.3.0). So, it allows updates like 1.2.4, 1.2.5, but not 1.3.0 or 2.0.0.
- Caret (^): The caret (^) symbol specifies a version range that allows for both minor and patch-level updates. When used in the package.json file, it means that you accept any new minor or patch-level releases while keeping the major version fixed.
For example, if you specify a dependency as "package": "^1.2.3", it means you will accept any version that is greater than or equal to 1.2.3 but less than the next major release (e.g., 2.0.0). So, it allows updates like 1.3.0, 1.4.0, 1.5.0, but not 2.0.0.
In summary, the tilde (~) allows for patch-level updates only, while the caret (^) allows for both minor and patch-level updates. It’s important to understand the version ranges you specify for dependencies to ensure compatibility and manage updates effectively in your projects.
Question:
What is the advantage of express?
Answer:
Express is a popular web application framework for Node.js. It offers several advantages that make it a preferred choice for building web applications. Here are some of the key advantages of using Express:
- Makes Node.js web application development fast and easy.
- Easy to configure and customize.
- Allows you to define routes of your application based on HTTP methods and URLs.
- Includes various middleware modules which you can use to perform additional tasks on request and response.
- Easy to integrate with different template engines like Jade, Vash, EJS etc.
- Allows you to define an error handling middleware.
- Easy to serve static files and resources of your application.
- Allows you to create a REST API server.
- Easy to connect with databases such as MongoDB, Redis, MySQL.
Question
What is a middleware?
Answer
A middleware, in the context of web development, is a function that sits between the client’s request and the server’s response. It helps handle and process incoming requests, modify them, and perform additional tasks before sending a response back to the client. Middleware functions are used to add functionality, perform checks, and modify the request or response in a web application.
Question
What are the various timing features of Node.js ?
Answer
Node.js provides several timing features that allow you to schedule and execute code at specific times or intervals. Here are some of the key timing features available in Node.js:
- setTimeout(): The
setTimeout()function allows you to schedule the execution of a callback function after a specified delay in milliseconds. It triggers the callback function once after the specified delay. - setInterval(): The
setInterval()function is similar tosetTimeout(), but it repeatedly triggers the execution of a callback function at a specified interval, repeatedly after the specified delay. - setImmediate(): The
setImmediate()function schedules the execution of a callback function to occur immediately after the current event loop phase, allowing other I/O events to be processed first. It is useful for executing code asynchronously but without introducing an additional delay. - process.nextTick(): The
process.nextTick()function is used to schedule a callback function to be executed on the next iteration of the event loop, immediately after the current operation completes. It provides a way to defer the execution of a callback until the next event loop cycle. - process.hrtime(): The
process.hrtime()function is used to measure the elapsed time in high-resolution. It returns a precise time measurement in the form of a tuple of seconds and nanoseconds. It is commonly used for performance measurements and benchmarking.
These timing features allow you to schedule code execution at specific times or intervals, handle asynchronous tasks, and measure performance in Node.js applications. They are useful for implementing timeouts, periodic tasks, asynchronous operations, and performance optimization.
Question
Explain what is Reactor Pattern in Node.js?
Answer
Reactor Pattern is an idea of non-blocking I/O operations in Node.js. This pattern provides a handler(in case of Node.js, a callback function) that is associated with each I/O operation. When an I/O request is generated, it is submitted to a demultiplexer.
This demultiplexer is a notification interface that is used to handle concurrency in non-blocking I/O mode and collects every request in form of an event and queues each event in a queue. Thus, the demultiplexer provides the Event Queue.
At the same time, there is an Event Loop which iterates over the items in the Event Queue. Every event has a callback function associated with it, and that callback function is invoked when the Event Loop iterates.
Question
Difference between find() & filter()?
Answer
The find() method locates the first matching value in the collection and returns it. Once a match is found, the search stops, and the method returns the identified value. It does not continue to check the remaining values in the collection.
Example:
On the other hand, the filter() method examines all the values in the collection, searching for matches. Instead of stopping at the first match, filter() continues scanning the entire collection and compiles all matching values into an array. This array containing all the matched values is then returned.
Example:
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