What happens if you await a function that does not return a Promise?
- It throws a syntax error
- The program crashes
- It works as expected
- It returns a rejected Promise
If you await a function that does not return a Promise, it will still work as expected. JavaScript automatically wraps the non-Promise value in a resolved Promise, allowing seamless integration of async/await with traditional synchronous functions.
A function that takes another function as an argument is called a __________ function.
- Callback
- Higher-order
- Nested
- Recursive
In JavaScript, a higher-order function is a function that takes one or more functions as arguments or returns a function. It enables the use of functions as data, promoting a more functional and modular approach.
What kind of exports are more conducive to effective tree shaking?
- Default exports
- Named exports
- All exports are treated equally by tree shaking.
- Both default and named exports
Tree shaking is more effective with named exports, as it can selectively include or exclude specific exports based on usage. Default exports can still be tree shaken, but named exports provide more granularity.
What is the result of using a Symbol as a key in a JSON object when using JSON.stringify?
- It serializes the symbol key along with its associated value.
- It ignores the symbol key and only serializes other enumerable properties.
- It throws an error since symbols cannot be used as keys in JSON objects.
- It converts the symbol key to a string and serializes it.
When using JSON.stringify, symbols are ignored, and only other enumerable properties are serialized. Symbols are not convertible to strings in this context.
Can dynamic imports be conditional? If so, what is a real-world use case?
- Yes, based on browser features
- No, always loaded unconditionally
- Yes, based on time of day
- No, only for large modules
Dynamic imports can be conditional, for example, based on browser features. This allows loading different code based on the capabilities of the user's browser, optimizing performance and providing a better user experience.
Which method is used to catch errors in a Promise?
- catchError
- errorHandler
- catch
- handleError
The correct method to catch errors in a Promise is the catch method. It is used to handle both synchronous and asynchronous errors that may occur during the execution of the Promise. By chaining the catch method to a Promise, you can specify a callback function to handle the errors and take appropriate actions.
Question 3: When setting up a mono-repo with multiple packages, how does ES6 module resolution impact the sharing of code across different packages?
- Facilitates code sharing through relative imports
- Hinders code sharing across packages
- Enables code sharing through global imports
- Requires a centralized package for sharing
In a mono-repo with multiple packages, using relative imports in ES6 modules can facilitate code sharing. It allows packages to import modules from one another directly, enhancing modularity and reusability. This approach avoids a centralized package and promotes a more decentralized and modular code organization.
How does the ES6 specification handle tail call optimization and what are its limitations in JavaScript implementations?
- ES6 specification doesn't explicitly mandate tail call optimization.
- It mandates tail call optimization, but its implementation varies.
- Tail call optimization is not supported in ES6.
- It is only applicable to specific cases in ES6.
In ES6, tail call optimization is mandated, but its implementation may vary across JavaScript engines. The limitation lies in inconsistent support across different environments, making it crucial to check engine compatibility when relying on this optimization.
Can destructuring assignment be used with arrays, and if so, how does it differ from object destructuring?
- Yes, and it works the same as with objects
- No, destructuring can only be used with objects
- Yes, but the syntax is different from object destructuring
- Yes, and it uses square brackets for the pattern
Destructuring assignment can be used with arrays in JavaScript. However, the syntax differs from object destructuring. With arrays, square brackets are used to indicate the pattern, making it distinct from object destructuring that uses curly braces.
What is the difference in execution timing between callbacks and Promises?
- Callbacks may lead to callback hell due to nested structures, affecting the execution sequence.
- Promises execute asynchronously, allowing better control over the flow of the program.
- Execution timing is the same for both callbacks and Promises.
- Callbacks always execute before Promises.
Promises provide a more straightforward approach to asynchronous programming, allowing developers to handle execution timing more efficiently. Callbacks, especially when nested, can lead to callback hell, making it challenging to manage the sequence of operations. This understanding is crucial for developers aiming to enhance code readability and manage asynchronous tasks effectively using Promises.