A common use case for WeakMap is to store ________ data for objects.
- metadata
- private
- public
- static
A common use case for WeakMap is to store metadata or additional information related to objects. Since WeakMap does not prevent object keys from being garbage collected, it's useful for storing data that should not interfere with garbage collection.
Consider a scenario where you are integrating third-party APIs in a web application. How would you ensure that API failures do not crash your application?
- Implementing robust error handling, logging, and potentially using circuit breakers
- Ignoring API errors and allowing the application to continue execution
- Restarting the application upon API failure
- Redirecting users to a generic error page on any API failure
Ensuring the resilience of the application against API failures involves implementing robust error handling mechanisms. This includes catching and logging errors, implementing retry strategies, and potentially using circuit breakers to temporarily halt requests in the event of persistent failures. Ignoring errors or restarting the application can lead to a degraded user experience and make troubleshooting difficult.
Prototype-based inheritance in JavaScript is an example of _________ inheritance, as opposed to class-based inheritance.
- Single
- Multiple
- Hierarchical
- Object
JavaScript uses prototype-based inheritance, where objects can inherit properties from other objects, forming a hierarchical chain of prototypes. This is different from class-based inheritance systems.
What potential issues might arise from using mixins in ES6, and how can they be mitigated?
- Name conflicts and unintended side effects
- Increased code complexity
- Difficulty in debugging
- Limited encapsulation
Using mixins in ES6 may lead to name conflicts and unintended side effects. To mitigate these issues, developers should adopt naming conventions, encapsulation, and thorough testing. This ensures that mixins enhance rather than hinder code maintainability.
In ES6, ________ methods are methods that are shared among all instances of a class.
- Static
- Prototype
- Instance
- Constructor
In ES6, static methods are associated with the class itself and not with instances. They are shared among all instances of the class.
What is the implication of using arrow functions in constructors?
- No implication
- this' is not bound to the instance
- this' is bound to the instance
- this' is bound to the constructor function
Arrow functions do not bind their own 'this', and using them in constructors can lead to 'this' being bound to the enclosing scope rather than the instance being created. This can result in unexpected behavior, making it not recommended to use arrow functions in constructors.
How are escape sequences like n treated in template literals?
- Treated as a newline character
- Ignored
- Treated as a literal backslash followed by 'n'
- Throws an error
In template literals, escape sequences like n are treated as newline characters. This allows for multi-line strings without the need for explicit line break characters.
In what order are tasks executed given JavaScript’s event loop and call stack mechanism?
- Based on the complexity of the task
- First In, First Out (FIFO) order
- Random order
- Last In, First Out (LIFO) order
Tasks in JavaScript are executed in a First In, First Out (FIFO) order. The event loop continually checks the call stack and executes tasks in the queue. This order ensures that tasks are processed in the sequence they are received, maintaining the integrity of the program's logic.
In a scenario where you need to convert an array of user objects into an array of names, which array method is the most suitable?
- map
- filter
- reduce
- forEach
In this scenario, the most suitable array method is map. The map method is designed for transforming each element of an array and returning a new array with the transformed values. It allows you to extract the names from the user objects efficiently.
In a scenario where you need to create private-like properties in an object, how would the Symbol type be used effectively?
- Using Symbol.createPrivateProperty
- Using Symbols as property names
- Using Object.defineProperty with Symbol
- Using private keyword
The correct option is using Symbols as property names. Symbols are unique and can be used as keys for object properties, providing a way to create private-like properties in an object. They help in avoiding naming conflicts and provide a level of encapsulation. Using Object.defineProperty with Symbol is a common approach to achieve this. The other options are incorrect as there is no direct Symbol.createPrivateProperty method, and the private keyword is not a standard feature in ES6 for creating private properties.