How does JavaScript handle implicit data type conversion?
- JavaScript automatically converts data types when performing certain operations, which can lead to unexpected results.
- JavaScript throws errors when trying to perform operations on different data types.
- JavaScript prohibits implicit data type conversion to ensure data consistency.
- JavaScript only allows explicit data type conversion using built-in functions.
JavaScript performs implicit data type conversion, also known as type coercion, when operators or functions are used with values of different data types. This can lead to unexpected behavior, so it's important to understand how type coercion works in JavaScript.
Developers can use npm deprecate [@] to mark a package or a specific version as deprecated, displaying a warning message ______ to any developers installing it.
- internally
- externally
- globally
- locally
When using npm deprecate, the correct option is externally. This means that a deprecation warning message will be displayed to any developers installing the package from outside the project.
How can the design of the Event Loop and Non-Blocking I/O lead to potential pitfalls in application behavior, such as callback hell or race conditions?
- The design ensures that such pitfalls are impossible in Node.js applications.
- Callback hell and race conditions are unrelated to the Event Loop and Non-Blocking I/O.
- Callback hell can occur due to deeply nested asynchronous callbacks, making code hard to read and maintain. Race conditions can happen when multiple asynchronous operations access shared resources without proper synchronization.
- Non-Blocking I/O eliminates all potential issues.
The design of the Event Loop and Non-Blocking I/O in Node.js can lead to challenges in application development. Callback hell can occur when developers create deeply nested asynchronous callbacks, making code hard to read and maintain. Race conditions can arise when multiple asynchronous operations access shared resources without proper synchronization, potentially leading to unexpected behavior. Understanding these pitfalls is crucial for writing efficient Node.js applications.
How can you create a private variable inside a JavaScript function?
- Use the 'private' keyword before declaring a variable.
- Declare the variable inside a function using 'var'.
- Use a function closure to encapsulate the variable within the function's scope.
- Use 'let' or 'const' to declare the variable inside a function.
To create a private variable in JavaScript, you can use a function closure. By defining a variable inside a function and not exposing it outside the function's scope, you can achieve encapsulation and create a private variable that is inaccessible from outside the function.
In JavaScript, the Symbol data type was introduced in ________.
- ECMAScript 2015 (ES6)
- JavaScript 1.5
- Node.js v10
- ESNext
The Symbol data type was introduced in ECMAScript 2015 (ES6). It allows you to create unique and immutable values that can be used as object property keys.
In Express.js, middleware functions have access to the request object, the response object, and the ______ function.
- next()
- send()
- app()
- router()
In Express.js, middleware functions have access to the request object (req), the response object (res), and a callback function commonly named next(). The next() function is used to pass control to the next middleware function in the chain.
You are tasked with developing a logging system for an Express.js application to log every incoming request. How would you implement middleware to log the details of every request made to the application?
- Create a middleware function that logs request details and use app.use to apply it globally to all routes.
- Include logging code within each route handler to log request details individually.
- Use a third-party logging library like Morgan and configure it within your Express.js application.
- Use JavaScript's built-in console.log within each route to log request details.
To log details of every incoming request in an Express.js application efficiently, you should create a dedicated middleware function that logs request details and use app.use to apply it globally to all routes. This centralizes logging and avoids duplicating code in each route handler. The other options are either less efficient or not recommended for production applications.
You are configuring a Node.js project and want to ensure that a certain command runs before your tests run each time. How would you configure this using the package.json file?
- Use the "pretest" script in the "scripts" section of the package.json file to specify the command that should run before tests.
- Include the command in the "description" field of the package.json file.
- Create a separate pretest.json configuration file.
- Use a comment in the test file to specify the pretest command.
To ensure a certain command runs before tests each time, you should use the "pretest" script in the "scripts" section of the package.json file. This script will be executed automatically before running tests when the npm test command is invoked. The other options are not standard ways to configure pretest actions.
You are developing a suite of unit tests for a service that interacts with an external API. How would you employ mocking and stubbing to ensure the tests are isolated and reliable?
- Mock the external API calls to simulate responses
- Stub all internal functions used in the service
- Avoid mocking and use real external API calls
- Mock only the database interactions
In unit testing, it's crucial to isolate the code being tested. To ensure tests are isolated and reliable when dealing with an external API, you should mock the external API calls. This allows you to control the responses and not rely on external services during tests. Stubbing internal functions is not the primary approach for isolating external API calls. Avoiding mocking by using real API calls can lead to unreliable and slow tests. Mocking the database, in this case, is unnecessary.
The fs.watch method is used to watch for changes in a file or a directory but may not be consistent across platforms due to its reliance on ______.
- inotify
- polling
- event-driven
- file system events
The fs.watch method relies on polling on some platforms to detect file and directory changes. This polling approach may not be consistent across platforms and can have performance implications.