You are maintaining a server that has strict security requirements. You need to allow cross-origin requests but with stringent restrictions. How can you implement CORS to fulfill these requirements while maintaining security?
- Set Access-Control-Allow-Origin to * and rely on server-side authentication.
- Implement preflight requests with custom headers and allow only authorized clients.
- Avoid using CORS and handle cross-origin requests through server-side scripting.
- Enable CORS for all origins and use server-side IP filtering.
To implement stringent security with CORS, you should use preflight requests with custom headers to allow only authorized clients. Option A is not secure as it allows any origin. Option C suggests avoiding CORS altogether, which may not be practical. Option D relies on IP filtering, which can be bypassed.
To install all the dependencies listed in the package.json file, the ______ command should be used.
- npm init
- npm add
- npm install
- npm create
To install all the dependencies listed in the package.json file, you should use the npm install command. It reads the dependencies specified in package.json and installs them. The other options are not used for this specific purpose.
You are developing a high-traffic e-commerce website. You need to implement a caching strategy to ensure that the load on the database is minimized, and the data retrieval is fast. Which caching strategy would be most suitable, and why?
- In-Memory Caching
- File-Based Caching
- Database Indexing
- No Caching
In this high-traffic scenario, In-Memory Caching would be the most suitable caching strategy. It stores frequently accessed data in RAM, ensuring rapid data retrieval and minimizing the load on the database server. File-Based Caching and Database Indexing may not offer the same level of performance improvement, and not using caching (No Caching) would increase the load on the database.
You are tasked with improving the reliability of a large codebase. Using Jest, how would you approach writing tests for functions with side effects like database calls or API requests?
- Use Jest's mocking capabilities to create mocks or spies for database and API calls.
- Skip testing functions with side effects; focus on pure functions.
- Manually perform database/API calls in tests to ensure real-world reliability.
- Use only integration tests for functions with side effects.
To improve reliability and isolate side effects, you should use Jest's mocking capabilities to create mocks or spies for database and API calls. This way, you can control and verify the behavior of these calls without involving the actual database or API. The other options may lead to unreliable tests or skipped testing.
Why is input validation crucial in web development?
- To ensure data is entered correctly.
- To make web forms look more attractive.
- To increase website loading speed.
- To prevent SQL injection.
Input validation is crucial in web development to prevent security vulnerabilities like SQL injection and to ensure that the data entered by users is correct and safe. It helps protect against malicious input and maintain data integrity.
When a package is listed under devDependencies, it means that the package is only required during the ________ of the application.
- development
- deployment
- testing
- runtime
When a package is listed under devDependencies, it means that the package is only required during the development of the application. These are typically tools and libraries used for development, such as testing frameworks, build tools, and linters. They aren't needed in the production or deployment environment.
You are tasked with developing a function to flatten a nested array structure. Which method would you use to flatten the arrays efficiently?
- Recursive function
- Array.prototype.flatMap()
- Nested loops
- Array.prototype.concat()
To efficiently flatten a nested array structure, you can use Array.prototype.flatMap(). It not only flattens the array but also allows you to transform its elements if needed. Using recursion is an option but can lead to stack overflow errors for deeply nested arrays.
In which of the following template engines can you write plain JavaScript code inside special tags?
- Mustache
- Handlebars
- Pug
- EJS (Embedded JavaScript)
EJS (Embedded JavaScript) allows you to write plain JavaScript code inside special tags <% %> or <%= %>. This feature is useful for executing JavaScript logic and generating dynamic content within templates. Mustache, Handlebars, and Pug have their own template syntax and do not support this feature in the same way.
Which of the following Node.js modules would you typically use to handle file uploads?
- fs
- http
- url
- multer
In Node.js, to handle file uploads, you would typically use the multer module. multer is a middleware for handling multipart/form-data, which is the format used for file uploads. The other options (fs, http, and url) are commonly used for different purposes, such as working with files, creating HTTP servers, and parsing URLs, respectively.
When using ES6+ modules, the import statement must be at the ________ of the file.
- bottom
- middle
- top
- end
When using ES6+ modules, the import statement must be at the top of the file. This is because ES6+ modules have a strict structure, and imports are processed before the module's code is executed. Placing the import statement at the top ensures that the imported dependencies are available throughout the module.