What is the significance of weak references in WeakMap and WeakSet with regards to memory management?
- Weak references in WeakMap and WeakSet allow for automatic garbage collection, preventing memory leaks.
- Weak references are irrelevant in the context of WeakMap and WeakSet, as they don't impact memory management.
- Weak references provide a way to create circular references, enhancing memory efficiency.
- Weak references ensure that the referenced objects are not eligible for garbage collection, preserving memory.
Weak references in WeakMap and WeakSet enable automatic memory management by allowing the garbage collector to reclaim objects that are no longer reachable.
What is the initial state of a JavaScript Promise when it is created?
- Pending
- Resolved
- Rejected
- Settled
When a Promise is created, it starts in the "Pending" state. This means that the Promise is neither fulfilled nor rejected. It's essentially in a pending state until the asynchronous operation it represents is completed.
In an async function, what happens to unhandled exceptions?
- They are automatically caught by the global error handler
- They cause the program to crash immediately
- They propagate to the nearest catch block
- They result in an unhandled promise rejection
Unhandled exceptions in an async function result in unhandled promise rejections. This can lead to unexpected behavior or crashes if not properly addressed. It's crucial to handle errors appropriately in async functions to ensure robust and error-resistant code.
In a project where a class needs to incorporate event-handling, logging, and validation behaviors, how would mixins and composition be used?
- By using inheritance and overriding methods in the class.
- By applying mixins through multiple inheritance.
- By using composition and creating separate classes for each behavior, then combining them.
- By using mixins and composing them into the class.
Mixins in ES6 can be applied by creating separate modules for each behavior (event-handling, logging, validation) and then composing these mixins into the class. This promotes code reusability and maintainability.
The __________ is responsible for executing the code, collecting and processing events, and executing queued sub-tasks.
- Callback Queue
- Event Loop
- Promise
- Closure
The Event Loop is a crucial part of JavaScript's concurrency model. It continuously checks the Call Stack and Callback Queue, ensuring the non-blocking execution of code.
When the call stack is busy, new requests get queued in the __________ for their turn to be processed.
- Callback Queue
- Microtask Queue
- Event Loop
- Task Queue
The correct option is Task Queue. When the call stack is occupied, new tasks are placed in the task queue to await their turn. The Event Loop manages the process of moving tasks from the task queue to the call stack. Understanding this mechanism is crucial for handling asynchronous operations effectively.
To create a pipeline of operations, functions can be composed using higher-order functions, known as __________.
- Callbacks
- Promises
- Closures
- Combinators
In functional programming, functions like compose or pipe are used as combinators to create a pipeline of operations by composing other functions. These are higher-order functions that take functions as arguments and return a new function that represents the composition of those functions.
Is it possible to create a shared Symbol that is accessible across different parts of your code?
- No, Symbols are always local to the scope they are created
- Yes, Symbols can be shared globally
- Only if Symbols are declared as constants
- Symbols can only be shared within the same function
Symbols can be shared globally by using the Symbol.for() method, which creates a shared Symbol registry accessible across different parts of your code. This promotes consistency and reusability.
In ES6 Modules, imports and exports must be ________, unlike in CommonJS where they can be dynamic.
- Explicit
- Implicit
- Dynamic
- Conditional
In ES6 modules, imports and exports must be explicit, meaning they are statically determined at compile-time. This allows for better tooling support and optimizations. CommonJS, on the other hand, allows dynamic imports and exports.
Arrow functions are not suitable for methods that need their own this context, such as ________ functions.
- Event
- Callback
- Constructor
- Recursive
Arrow functions do not have their own this context, making them unsuitable for methods that need access to the object's this value. Constructor functions, which initialize objects and rely on this, should not be implemented using arrow functions.