Which of the following is the correct way to declare a variable in JavaScript?
- var x = 10;
- x := 10;
- int x = 10;
- declare x = 10;
In JavaScript, variables can be declared using the var keyword. The other options are either used in different programming languages or are not valid syntax in JavaScript.
Which of the following is the correct way to parse JSON in the body of a request in Express.js?
- app.use(express.json())
- app.use(body.parse())
- app.use(request.json())
- app.parse(json)
To parse JSON in the body of a request in Express.js, you should use app.use(express.json()). This middleware is used to parse JSON data in the request body. The other options do not represent the correct way to parse JSON in Express.js.
You are working on a project that has several outdated packages with known vulnerabilities. What approach would you take to update those packages while ensuring the stability of the project?
- Update all packages to their latest versions immediately
- Review the changelogs of outdated packages, perform incremental updates, and thoroughly test each update
- Ignore the outdated packages as they may not impact the project
- Downgrade the Node.js version to maintain package compatibility
The correct approach is to review the changelogs of outdated packages, perform incremental updates, and thoroughly test each update. This ensures that updates do not introduce breaking changes and maintain project stability.
When implementing JWT, where is the token commonly stored for subsequent requests?
- In a cookie
- In a URL query parameter
- In a request header
- In a hidden form field
In JWT (JSON Web Tokens), the token is commonly stored in a request header, specifically in the Authorization header using the Bearer scheme. This method is considered secure and widely adopted. Storing the token in a cookie or URL query parameter can have security risks.
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.
Express.js middleware functions have access to the ______ object, the ______ object, and a next function in their callback function parameters.
- request, response
- response, request
- req, res
- req, next
In Express.js middleware functions, the callback function parameters typically include req (the request object) and res (the response object). Additionally, you can use a next function to pass control to the next middleware function in the pipeline. This allows you to manipulate the request and response objects or perform actions before sending a response to the client.