In ES6, which method is commonly used as a higher-order function for arrays?
- map()
- concat()
- reduce()
- slice()
The map() method in ES6 is commonly used as a higher-order function for arrays, allowing the transformation of each element with a provided function.
What is tail call optimization in recursive functions and how is it handled in ES6?
- Tail call optimization is a technique where the JavaScript engine optimizes recursive functions to avoid stack overflow errors. In ES6, tail call optimization is not explicitly mandated, but certain engine implementations may provide it.
- Tail call optimization in ES6 can be achieved through the use of proper coding practices, such as making the recursive call the last operation in the function and ensuring no additional processing is performed after the recursive call.
- ES6 introduces the concept of proper tail calls (PTC), allowing some recursive functions to be optimized for tail calls. This optimization is not universally supported across all JavaScript engines.
- Tail call optimization is automatically applied to all recursive functions in ES6, ensuring that stack overflow errors are mitigated, and the recursive calls are optimized for better performance.
Proper tail calls in ES6 involve making the recursive call the last operation in a function. While not all recursive calls benefit from tail call optimization, adhering to PTC principles can enhance performance in situations where tail call optimization is applied.
Which of the following is not a state of a Promise?
- Completed
- Fulfilled
- Rejected
- Pending
"Completed" is not a standard state of a Promise. The valid states are "Pending," "Fulfilled," and "Rejected." A Promise is initially in the "Pending" state and transitions to either "Fulfilled" or "Rejected" based on the outcome of the asynchronous operation it represents.
For an analytics dashboard that requires data transformation, how would higher-order functions streamline this process?
- map
- reduce
- filter
- forEach
The correct option is map. map is used for transforming each element of an array and creating a new array with the transformed values. It is ideal for data transformation tasks in scenarios like an analytics dashboard.
Consider a web application where you need to apply multiple transformations to user input. How would functional composition enhance this process?
- Improved Reusability and Modularity
- Increased Complexity and Maintenance
- Streamlined Debugging and Error Handling
- Reduced Code Duplication and Enhanced Readability
Functional composition allows breaking down complex transformations into smaller, reusable functions. This promotes code modularity, simplifies debugging, and enhances readability by reducing code duplication. It streamlines the development process by composing functions to perform various transformations efficiently. This approach leads to more maintainable and scalable code.
How can destructuring assignment be effectively used in React components to handle props and state?
- It cannot be used with React components
- It simplifies access to props and state values
- It makes React components slower
- It is only applicable to class components
Destructuring assignment is commonly used in React components to handle props and state efficiently. By extracting specific values from the props and state objects using destructuring syntax, developers can improve code readability and make component logic more concise. This practice simplifies the process of accessing and using props and state values within the component, contributing to better-organized and more maintainable React code.
How do enhanced object literals in ES6 facilitate the assignment of variables as properties of objects?
- Dynamic Assignment
- Property Binding
- Object Linking
- Variable Embedding
In ES6, enhanced object literals allow dynamic assignment of variables as properties using square brackets. This feature is especially useful when the property name needs to be determined at runtime. It promotes a more flexible and concise way of defining object properties.
To export multiple features from a single module, use export { feature1, feature2 as _______ };.
- alias
- as
- export
- feature2
To export multiple features from a single module, use export { feature1, feature2 as alias }; where as alias provides an optional alias for the exported feature, making it clear when imported.
How do dynamic imports affect the performance of a web application?
- Increase Performance
- Decrease Performance
- No Impact
- Depends on Implementation
Dynamic Imports can potentially decrease the initial load time of a web application by loading modules asynchronously. This can lead to improved performance, especially in scenarios where not all modules are required immediately. However, the actual impact depends on various factors, such as network conditions and how dynamic imports are implemented.
What happens when an iterator's next() method returns an object with done: true?
- It means the iteration is complete, and further calls to next() will throw an error
- It indicates an error in the iteration process
- It signals an infinite loop in the iteration
- It signifies that there are more elements to be iterated
When the next() method returns an object with done set to true, it indicates that the iteration has reached its end, and there are no more elements to be processed. Subsequent calls to next() will continue to return objects with done: true, providing a clear signal that the iteration is complete.