What syntax is used to handle the promise returned by a dynamic import?
- await import('module')
- import('module').then()
- dynamicImport('module')
- import('module').catch()
The correct syntax to handle the promise returned by a dynamic import is import('module').then(). You use the then method to perform actions once the module has been successfully loaded. The catch method can be used for error handling if the dynamic import fails.
In functional programming, what is the recommended way to handle functions with side effects?
- Embrace side effects
- Minimize side effects
- Avoid functions altogether
- Encourage side effect propagation
In functional programming, it is recommended to minimize side effects. While it may be challenging to eliminate them entirely, minimizing side effects helps maintain the purity of functions and promotes a more declarative and predictable coding style. This approach contributes to better code maintainability and understandability.
What is a common pitfall when chaining multiple asynchronous operations using Promises?
- Not handling errors within each promise's chain.
- Mixing Promises with Callbacks.
- Using async/await inside a promise chain.
- Chaining promises without returning a new promise.
One common pitfall is forgetting to return a new promise when chaining promises. If a promise is not returned from each .then() callback, subsequent promises won't wait for the asynchronous operation to complete, potentially leading to unexpected behavior.
To pause and resume a generator function, the _________ keyword is used within the function body.
- yield
- await
- pause
- resume
In a generator function, the yield keyword is used to pause and resume the function's execution. It allows the generator to produce a sequence of values over time. The other options are not relevant to the purpose of pausing and resuming a generator.
Which of the following is a built-in higher-order function in JavaScript?
- map()
- add()
- concat()
- subtract()
The map() function in JavaScript is a built-in higher-order function that is commonly used to transform elements of an array. It takes a function as an argument and applies it to each element of the array.
In a scenario where a function calculates the total price of items in a cart, how would making this function pure affect its implementation?
- It would introduce side effects
- It would improve testability and predictability
- It would slow down the function execution
- It would require additional dependencies
Making the function pure in this scenario would involve removing external dependencies and ensuring that the function's output depends only on its input. This enhances testability and predictability, making the function easier to reason about and test in isolation. It also helps in avoiding side effects, which is a key characteristic of pure functions.
Can you reassign a new array or object to a variable declared with const?
- Yes, always
- Yes, but with restrictions
- No, it will result in an error
- Only if the variable is declared as a global constant
Variables declared with const cannot be reassigned to a new reference, whether it's an array, object, or any other data type. However, it's crucial to understand that this rule applies only to the reference itself, not the content of the variable. The content, if mutable (e.g., an object's properties), can still be modified.
How does recursion differ from iteration in JavaScript?
- Recursion is more memory-efficient
- Recursion uses a stack, while iteration uses a loop
- Recursion is slower than iteration
- Recursion is not supported in JavaScript
Recursion involves a function calling itself, creating a stack of function calls. In contrast, iteration uses loops for repetitive tasks. Understanding these differences is essential in choosing the right approach.
A common use case for currying is to create more _________ versions of existing functions.
- Specialized, Generalized, Efficient, Complex
- Efficient, Complex, Generalized, Specialized
- Complex, Generalized, Specialized, Efficient
- Specialized, Efficient, Generalized, Complex
Currying allows the creation of more generalized versions of functions. By partially applying arguments, you can reuse and specialize functions for various scenarios.
Is it possible to declare a variable with let or const in a for-loop and access it outside of the loop?
- Yes, you can access it outside the loop
- No, it's not accessible outside the loop
- Only let variables are accessible
- Only const variables are accessible
Variables declared with let or const in a for-loop are accessible outside of the loop in which they are declared. They have block scope, which means they are confined to the nearest enclosing curly braces, allowing them to be accessed outside the loop.