Which of the following is the primary role of middleware in Express.js?
- Handling client-side routing
- Handling server-side routing
- Managing HTTP requests and responses
- Creating database schemas
The primary role of middleware in Express.js is to manage HTTP requests and responses. Middleware functions are executed in the order they are defined in the Express application and can perform various tasks such as authentication, logging, and modifying request/response objects. They play a crucial role in the request/response cycle.
Which keyword is used to export multiple things from a module in JavaScript?
- import
- export
- require
- module
In JavaScript, the export keyword is used to export multiple things from a module. It allows you to specify which functions, objects, or variables should be accessible from outside the module. The import keyword is used for importing from modules, not exporting. The require and module keywords are used in CommonJS, a different module system.
Where should you ideally store your static files like images, CSS, and JavaScript in an Express.js project?
- In the project root directory
- In a dedicated static directory
- Inside the node_modules directory
- In a separate database
In an Express.js project, it's a best practice to store your static files like images, CSS, and JavaScript in a dedicated static directory. This helps organize your project and makes it clear which files are intended to be served statically. Storing them in the project root, node_modules, or a database is not a recommended practice for serving static files.
How does JavaScript handle circular dependencies between modules?
- JavaScript throws an error and does not allow circular dependencies.
- JavaScript allows circular dependencies, and they are resolved at runtime.
- JavaScript handles circular dependencies by allowing them but ensuring that each module loads only once.
- Circular dependencies are not supported in JavaScript.
JavaScript allows circular dependencies, but it ensures that each module is only executed once. This is achieved through a mechanism called "module caching."
When handling errors in an async function, if an error is not caught within the function, it will cause the returned Promise to be in a ________ state.
- Pending
- Fulfilled
- Rejected
- Completed
When an uncaught error occurs in an async function, the returned Promise will be in a "Rejected" state. In the Promise lifecycle, it can start as "Pending," move to "Fulfilled" upon success, or "Rejected" upon an error.
What is the significance of a returned inner function having access to the outer function's variables even after the outer function has executed?
- It's a programming error and should be avoided.
- It has no significance; it's just a quirk of JavaScript.
- It allows data encapsulation and creates private variables, aiding in maintaining state and data privacy.
- It has no practical use in JavaScript.
The significance of a returned inner function having access to the outer function's variables after the outer function has executed is that it enables data encapsulation and the creation of private variables. This is crucial for maintaining state and data privacy in JavaScript applications.
When are CORS preflight requests sent by the browser?
- Before making certain types of requests
- After a successful request
- Randomly to check server compatibility
- Only when cookies are involved
CORS preflight requests are sent by the browser before making certain types of requests, specifically those that could have an impact on server security or state. These preflight requests are used to check with the server if the actual request (e.g., a cross-origin POST request with custom headers) is allowed, ensuring server compatibility and security.
You are working on a Node.js project with a team, and you notice that the package-lock.json file is frequently causing merge conflicts. How would you resolve or minimize such conflicts while ensuring consistent dependency resolution?
- Remove the package-lock.json file entirely
- Use Yarn instead of npm
- Use a tool like npm ci and enforce it in your team's workflow
- Manually edit the package-lock.json file in case of conflicts
To minimize package-lock.json merge conflicts, you should use a tool like npm ci in your team's workflow. npm ci installs dependencies based on the package-lock.json and ensures consistent dependency resolution. Options 1 and 2 are not recommended, and option 4 is not a practical solution.
What is the difference between chaining multiple .then() methods and using multiple await expressions?
- Chaining .then() is more efficient for error handling
- Chaining .then() is better for readability
- Using multiple await expressions allows better error propagation
- Using multiple await expressions guarantees faster execution
When using await expressions, errors can be propagated using standard try/catch blocks, which allows for more granular and flexible error handling. Chaining multiple .then() methods can lead to less readable and maintainable code when dealing with multiple asynchronous operations. It's not a question of efficiency or speed but rather about readability and error handling.
The prototype of an instance object in JavaScript is found using the ______ property.
- __proto__
- instanceOf
- type
- parent
The __proto__ property is used to access the prototype of an instance object in JavaScript. This is how objects inherit properties and methods from their constructor's prototype.