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.
Which of the following is a correct way to declare a function in JavaScript?
- function myFunction() => { ... }
- func myFunction() { ... }
- def myFunction() { ... }
- myFunction => { ... }
In JavaScript, functions are declared using the function keyword, followed by the function name and parentheses. The correct syntax is function myFunction() { ... }. The other options are not valid ways to declare functions in JavaScript.
What is the main purpose of using 'describe' and 'it' blocks in Mocha?
- Defining Test Suites and Test Cases
- Creating HTML Elements
- Importing External Libraries
- Generating Random Numbers
In Mocha, 'describe' blocks are used for defining test suites or groups of related test cases, and 'it' blocks are used for specifying individual test cases. This helps in organizing and structuring your test suite, making it more readable and maintainable.
In JavaScript, closures are crucial for functional programming as they facilitate the creation of ________.
- Private Variables
- Callbacks
- Promises
- Modules
Closures in JavaScript allow the creation of private variables within functions. This encapsulation is essential for functional programming, where data should be isolated and not directly accessible from outside the function.
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.
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.