If a variable declared with const is an object or array, its properties can still be ________.
- Modified
- Deleted
- Reassigned
- Hidden
In JavaScript, when a variable is declared with const, it means the reference to the object or array is constant, not the actual content. Therefore, you can't reassign the variable, but you can still modify, delete, or add properties to the object or array.
Describe a scenario where dynamic imports would be beneficial in a server-side JavaScript environment.
- In an environment where all server-side code is loaded upfront.
- When server-side modules need to be loaded on-demand based on specific requests.
- Only in scenarios where server-side code is minimal.
- Use static imports to include all server-side modules during startup.
Dynamic imports in a server-side JavaScript environment are beneficial when specific modules are required on-demand, such as handling different types of requests. This helps optimize resource usage and improve response times in scenarios with varying workloads.
How do you remove an item from a Map in ES6?
- delete method
- remove method
- pop method
- discard method
In ES6, you can use the delete method to remove an item from a Map. This method takes the key as an argument and removes the corresponding key-value pair from the Map.
How do prototype delegation and proto property in ES6 object literals work?
- They are unrelated concepts in ES6.
- Prototype delegation is achieved through the proto property.
- The proto property is used for inheritance in object literals.
- Prototype delegation is an obsolete feature in ES6.
In ES6 object literals, the proto property is used to establish prototype delegation and achieve inheritance. The proto property allows an object to inherit properties and methods from another object, forming a prototype chain. This mechanism facilitates code reuse and promotes a more modular and extensible design. It is important to note that the proto property is considered an internal implementation detail, and using Object.create() is the recommended approach for explicit prototype delegation.
What is the primary advantage of using dynamic imports in JavaScript?
- Code Splitting
- Improved Code Readability
- Faster Execution
- Enhanced Browser Compatibility
Dynamic Imports in JavaScript allow for efficient code splitting. By loading only the modules that are needed at runtime, it improves the performance of the application, especially in large projects where not all code is required on every page.
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.