How does a pure function handle dependencies or external variables?
- Manages dependencies internally
- Avoids external dependencies
- Handles dependencies through callbacks
- Utilizes global variables
In a pure function, dependencies are avoided to maintain purity. External variables could introduce side effects, violating the principle of purity.
Can a generator function yield another generator function? If so, how is it achieved?
- No, it is not possible
- Yes, using yield* keyword
- Yes, using async keyword
- Yes, using yield keyword
Yes, a generator function can yield another generator function using the yield* keyword. This allows for the delegation of the generator control, enabling the composed use of generators within generators. This feature enhances the modularity and reusability of generator functions.
How do you create a new object that inherits from an existing object in ES6?
- Object.create()
- Object.inherit()
- Object.extend()
- Object.instantiate()
In ES6, the Object.create() method is used to create a new object that inherits from an existing object. It sets up prototype chaining, allowing the new object to inherit properties and methods from the existing one.
How does the Promise.all method interact with async/await?
- Waits for all promises to resolve and then proceeds
- Rejects if any of the promises reject
- Executes promises concurrently
- Resolves immediately without waiting
Promise.all waits for all promises to resolve successfully before proceeding. If any of the promises reject, the entire Promise.all rejects. This makes it useful when you have multiple asynchronous operations that can be executed concurrently and you want to wait for all of them to complete. When combined with async/await, you can use it to await multiple asynchronous operations concurrently.
In a situation where a web application needs to fetch data from an API and handle both the data response and possible errors, what are the best practices using Promises?
- Using async/await
- Promise.catch
- Using try/catch
- Using setTimeout
The best practice in handling both successful data responses and errors with Promises is by using async/await. This allows for cleaner and more readable code, making it easier to handle both resolved and rejected promises in a structured and organized manner.
When optimizing a web application for performance, considering the need for tree shaking and module caching, which module system offers more advantages?
- ES6 Modules
- CommonJS
- Both have similar performance optimizations
- Depends on the specific use case
ES6 Modules provide better support for tree shaking, a process that eliminates unused code during the build, resulting in smaller bundles and improved performance. Additionally, ES6 Modules support native module caching, further enhancing performance by reducing redundant module loading.
How does the lack of enumeration in WeakMap and WeakSet impact their use cases?
- Lack of enumeration in WeakMap and WeakSet prevents direct access to their elements.
- Enumeration is not essential in WeakMap and WeakSet, as they are designed for scenarios where enumeration is not needed.
- Lack of enumeration provides an added layer of security, making it difficult for external code to access the internal state of these structures.
- Enumeration is not relevant in the context of WeakMap and WeakSet, as their primary use is for memory management.
Lack of enumeration allows these structures to be more suitable for scenarios where privacy and encapsulation are critical.
In a for...of loop, the _________ method of an iterable object is called to retrieve values.
- next()
- iterate()
- forEach()
- value()
In a for...of loop, the next() method of an iterable object is called to retrieve values. The next() method is automatically called in each iteration of the loop, returning an object with the value property containing the current value.
In what way does the Spread Operator interact with iterables?
- Spreads the iterable elements into a new array
- Converts the iterable into a string
- Ignores the iterable elements
- Creates a deep copy of the iterable
The Spread Operator (...) in ES6 is used to spread the elements of an iterable (e.g., an array) into a new array. It provides a concise way to concatenate arrays, create shallow copies, and pass array elements as function arguments.
What is the default behavior of this at the top level in ES6 Modules, as opposed to CommonJS modules?
- Lexical scoping
- Dynamic scoping
- No scoping
- Global scoping
In ES6 Modules, the this keyword behaves according to lexical scoping, meaning it retains the value of this from the surrounding scope. This is different from CommonJS modules, where this refers to the exports object.
In Promises, the _______ function is used to transition a promise into a resolved state, while _______ is used for rejection.
- resolve
- then
- reject
- catch
The correct option is 'resolve.' The resolve function transitions a promise into a resolved state, fulfilling the promise. On the other hand, the 'catch' function is used to handle rejection and is associated with the 'reject' state. The 'then' function is used for chaining and handles both fulfillment and rejection.
How does garbage collection in JavaScript affect WeakSet?
- WeakSet does not participate in garbage collection
- WeakSet triggers garbage collection on its own
- Garbage collection has no impact on WeakSet
- WeakSet entries are explicitly removed during garbage collection
Garbage collection has no impact on WeakSet. Unlike traditional sets, WeakSet does not prevent the referenced objects from being garbage-collected, making it useful in scenarios where you don't want to retain objects solely because they are part of a set.