In a project management tool, you need to ensure each task is unique but also maintain their insertion order. Which data structure would you use?
- Set
- Array
- WeakSet
- Map
In this case, an Array is the most appropriate choice. It allows you to maintain the order of tasks while ensuring uniqueness. Unlike Set, which only stores unique values without any specific order, an Array meets both requirements for this project management tool.
If you are required to iterate over a collection of objects representing users and perform an action on each, how would a for...of loop benefit over other loops?
- for loop
- for...in loop
- forEach loop
- for...of loop
The correct option is the for...of loop. It is specifically designed for iterating over iterable objects and works well with arrays and other collections. It directly provides the values, avoiding the need for indexing and making the code more readable. This is especially beneficial when iterating over objects representing users, as it simplifies the syntax and enhances code clarity.
Consider a scenario where you have to implement a function to compute factorial numbers. How would ES6 features enhance the implementation of this recursive function?
- Utilize the let and const declarations for improved variable scoping and clarity.
- Apply the var declaration for simplicity and compatibility.
- Use the arrow function syntax for concise and expressive code.
- Implement the function using the function keyword for better readability.
ES6 features like let and const provide block-level scoping, enhancing the clarity of variables in the recursive factorial function. The arrow function syntax also contributes to code conciseness, making the implementation more elegant. The other options either introduce potential issues or miss the advantages of ES6 features.
The _________ method in Promise chaining is used to catch any errors that occur during the execution of the promise.
- reject()
- catch()
- handle()
- error()
The correct method is catch(). It is used in promise chaining to handle any errors that may occur during the execution of the promise. It is a best practice to include a catch() block to handle errors in promise chains.
What types of collections can the for...of loop iterate over in JavaScript?
- Arrays
- Objects
- Strings
- All of the above
The for...of loop can iterate over iterable objects like arrays, strings, maps, sets, etc. However, it does not work with non-iterable objects like plain objects (use for...in for objects).
In order for tree shaking to work effectively, the module bundler must support _______ analysis.
- Static
- Dynamic
- Runtime
- Bundle
The correct option is (a) Static. Effective tree shaking relies on static analysis of the code by the module bundler. It involves analyzing the code without executing it, allowing the bundler to determine which parts of the code are unreachable and can be safely eliminated during the bundling process.
Can dynamic imports be used in place of traditional static imports?
- Yes, always
- No, never
- It depends on the use case
- Only in Node.js environments
Dynamic imports cannot always replace traditional static imports. They are suitable for scenarios where modules are needed dynamically at runtime, but static imports are still necessary for modules required during the application's initialization.
How does dynamic import (import()) differ from static import (import ... from) in ES6?
- Deferred loading at runtime
- Resolved during compilation
- Allows importing entire modules as a single object
- Used for importing only specific exports
Dynamic import allows loading a module at runtime, which can be beneficial for code splitting and lazy loading. Static import, on the other hand, is resolved during compilation.
Which method is essential for an object to be an iterator?
- next() method
- getIterator() method
- iterate() method
- forEach() method
An iterator in JavaScript must implement the next() method. This method is called on each iteration and should return an object with properties like value and done, indicating the next value in the sequence and whether the iteration is complete.
How do dynamic imports interact with tree shaking in modern JavaScript bundlers?
- Enhances tree shaking
- Impedes tree shaking
- No interaction
- Works only in development mode
Dynamic imports enhance tree shaking by enabling the removal of unused code during the bundling process. Tree shaking is more effective as it can analyze the dynamic imports and eliminate dead code paths, leading to smaller bundle sizes.