In JavaScript, the import statement cannot be used in ________.
- functions
- classes
- conditionals
- loops
In JavaScript, the import statement cannot be used inside conditionals (e.g., if statements or loops). It must be used at the top level of a module. This is because module imports are processed before the code is executed, and conditionals are not allowed to change the module structure dynamically.
What is the primary purpose of running the npm init command in a Node.js project?
- To install Node.js
- To create a new Node.js project
- To update Node.js packages
- To uninstall Node.js
The primary purpose of running npm init in a Node.js project is to create a new Node.js project. This command initializes a package.json file, which is essential for managing project dependencies and configurations. It does not install or uninstall Node.js itself.
How do you correctly implement a middleware function in Express.js?
- Define a function with the signature (req, res)
- Use the middleware() keyword before a route definition
- Import the express-middleware module
- Add a next() function to the route handler
To correctly implement a middleware function in Express.js, you define a function with the signature (req, res). This function can also take an optional next parameter if you want to pass control to the next middleware in the stack. The (req, res) signature allows you to access and modify the request and response objects.
What is the main difference between SQL and NoSQL databases regarding data structure?
- SQL databases are faster than NoSQL databases.
- SQL databases are faster than NoSQL databases.
- SQL databases are limited to relational data, while NoSQL databases can handle any data type.
- SQL databases are open source, while NoSQL databases are proprietary.
The main difference is that SQL databases use a structured, tabular format for data storage, adhering to a fixed schema, while NoSQL databases use various flexible data models, making them suitable for unstructured or semi-structured data. SQL databases are not inherently faster, and the choice depends on the specific use case.
How can you match routes with a specific pattern in Express.js?
- app.pattern('/route', callback)
- app.match('/route', callback)
- app.use('/route', callback)
- app.get('/route', callback)
In Express.js, you can use the app.get('/route', callback) method to match routes with a specific pattern. The get method is used to handle HTTP GET requests and is often used to define routes with specific patterns. The other options do not represent the standard way to define route patterns in Express.js.
In which scenario would denormalization be considered a suitable option for query optimization?
- When you want to minimize data redundancy and improve data integrity.
- When you want to improve query performance, even at the cost of some data redundancy and update anomalies.
- Denormalization is never considered a suitable option for query optimization.
- When you want to reduce the size of the database.
Denormalization is considered when you want to optimize read-heavy queries and reduce the number of JOIN operations. It involves introducing redundancy to improve query performance, but it can lead to data anomalies.
In JavaScript, a variable declared without the var, let, or const keyword inside a function becomes a property of the ________ object.
- "window"
- "global"
- "local"
- "this"
In JavaScript, a variable declared without the var, let, or const keyword inside a function becomes a property of the "global" object. This can lead to unexpected behavior, so it's important to declare variables properly.
What strategies can be employed to optimize aggregation queries in NoSQL databases like MongoDB?
- Aggregation queries in NoSQL databases like MongoDB can be optimized by using the aggregation framework provided by MongoDB, creating proper indexes on fields used in aggregation stages, leveraging server resources efficiently, and using projection to limit the output data size.
- Aggregation queries in NoSQL databases cannot be optimized.
- Aggregation queries in NoSQL databases can only be optimized by using raw database queries with no additional strategies.
- Aggregation queries in NoSQL databases should be avoided altogether.
Aggregation queries in NoSQL databases can be resource-intensive, but they can be optimized using MongoDB's aggregation framework and other techniques to improve query performance.
How can you handle CORS to allow cookies to be included in requests?
- Access-Control-Allow-Origin: *
- Access-Control-Allow-Credentials: true
- Access-Control-Allow-Headers: *
- Access-Control-Allow-Methods: GET, POST
To allow cookies to be included in CORS requests, you should set the Access-Control-Allow-Credentials header to true. The other options are related to different aspects of CORS, but they don't specifically enable cookie handling.
What is the primary use of the spread operator in JavaScript?
- To merge arrays and objects
- To create a new array with the same elements
- To create a deep copy of an object
- To remove elements from an array
The primary use of the spread operator (...) in JavaScript is to merge arrays and objects. It can also be used to clone an array or object, effectively creating a new array or object with the same elements or properties.