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.
Which of the following is the primary goal of input sanitization?
- Enhancing user experience.
- Ensuring data accuracy.
- Preventing cross-site scripting (XSS) attacks.
- Optimizing database performance.
The primary goal of input sanitization is to prevent cross-site scripting (XSS) attacks. It involves removing or encoding potentially dangerous characters from user input to ensure that it cannot be executed as script on a web page, thus enhancing web security.
When using the map method on an array in JavaScript, the original array ______ be mutated.
- may
- will
- must
- can't
When using the map method on an array in JavaScript, the original array can't be mutated. The map method creates a new array with the results of calling a provided function on every element in the original array without changing the original array itself.
Which of the following is a suitable method to prevent variable leakage in the global scope?
- Using the var keyword to declare variables.
- Using immediately-invoked function expressions (IIFE).
- Using global variables exclusively.
- Using let and const keywords to declare variables.
Using immediately-invoked function expressions (IIFE) is a common technique to prevent variable leakage into the global scope. It encapsulates variables within a function scope, avoiding global pollution. The other options do not address this concern effectively.
How can you install ESLint in your Node.js project?
- Using npm or yarn: npm install eslint --save-dev or yarn add eslint --dev
- Downloading it from the official website
- Installing it globally using npm install -g eslint
- Adding it directly to your HTML file
You can install ESLint in your Node.js project using npm or yarn by running the command npm install eslint --save-dev or yarn add eslint --dev. This ensures that ESLint is added as a development dependency for your project.
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.