Consider a situation where you have an array of user objects. How would you implement an iterator to selectively process only certain users?
- Use the filter method to create a new array with the selected users
- Implement a custom iterator with a conditional statement inside the next method
- Use the map method to selectively process users
- Utilize the reduce method to iterate and selectively process users
Implementing a custom iterator is a powerful approach in this scenario. By creating a custom iterator, you have fine-grained control over the iteration process, allowing you to selectively process specific users based on the conditions defined in the iterator's next method.
If you have a configuration object that should not be altered during the execution of a program, how would you declare it using ES6 syntax?
- Declare using let
- Declare using const
- Declare using var
- Declare using readonly (ES6 feature)
You would declare the configuration object using const, as it ensures the object remains constant throughout the program execution, preventing unintended changes.
What method is used to specify the code to execute after a Promise is fulfilled?
- then()
- catch()
- resolve()
- reject()
The then() method is used to specify the code that should be executed after a Promise is fulfilled. It allows you to handle the successful resolution of a Promise and work with the result.
What is the impact of ES6 Modules on asynchronous loading and module bundling tools compared to CommonJS?
- Increased bundle size due to module encapsulation
- Improved parallel loading of modules
- Slower loading of dependencies
- Limited compatibility with bundling tools
ES6 Modules support asynchronous loading and enable parallel loading of modules, improving performance. Additionally, they work seamlessly with modern module bundlers, leading to more efficient bundling and reduced bundle size.
If you are refactoring a set of classes representing different types of user accounts in a system, how would constructors and super assist in initializing properties common to all account types?
- Utilize constructors in each class without the super keyword.
- Rely on global variables to initialize common properties.
- Use the super keyword to invoke the parent class constructor for shared properties.
- Avoid constructors altogether and rely on setter methods.
Constructors and the super keyword are essential in refactoring user account classes. Constructors help initialize class-specific properties, while super facilitates the invocation of the parent class constructor, ensuring that common properties are appropriately initialized across all account types.
Default parameters can be combined with object destructuring to construct complex default values.
- Object Literals
- Object Destructuring
- Object Prototypes
- Object Methods
ES6 introduced object destructuring, allowing you to extract values from objects easily. When combined with default parameters, it becomes a powerful feature for defining functions with complex default values. The correct option, "Object Destructuring," signifies this technique.
In ES6, class properties are often initialized inside the ________ method.
- initialize
- constructor
- create
- new
Class properties in ES6 are commonly initialized inside the constructor method. This allows you to set initial values for properties when an object is created.
Can a for...of loop be used to iterate over a generator function's yielded values?
- Yes, a for...of loop can iterate over the yielded values of a generator function.
- No, for...of loops are not compatible with generator functions.
- Yes, but it requires additional syntax.
- No, generator functions can only be iterated using for...in loops.
Yes, a for...of loop can be used to iterate over a generator function's yielded values. The for...of loop automatically iterates over the values yielded by the generator, making it a convenient and readable way to consume generator values.
How can you handle potential undefined values when destructuring an object?
- Ignore the value
- Provide default values
- Throw an error
- Use try-catch block
When destructuring an object, you can provide default values to handle potential undefined values. If the property is not present in the object, the default value will be used. This helps prevent errors due to missing properties.
When higher-order functions are used for asynchronous programming, they often involve __________ to handle future results.
- Callbacks
- Closures
- Promises
- Observables
Promises are a type of higher-order function used for handling asynchronous operations in JavaScript. They provide a clean and structured way to work with asynchronous code by representing a value that might be available now, in the future, or never.
Static properties are useful for storing data that __________ across all instances of the class.
- varies
- fluctuates
- persists
- changes
Static properties in a class are shared among all instances, ensuring that the data remains consistent across different objects created from the same class. This is particularly useful for information that should be common to all instances.
Tree shaking can fail to eliminate unused code if modules are dynamically _______ at runtime.
- Imported
- Exported
- Loaded
- Unloaded
The correct option is (c) Loaded. Tree shaking may fail if modules are dynamically loaded at runtime. Dynamically loading modules introduces uncertainty about which modules will be used, making it challenging for the module bundler to perform effective tree shaking.