Describe the flow of execution in a JavaScript program that includes both synchronous logging and asynchronous API calls.
- The synchronous code is executed first, followed by the asynchronous API call. The API call is offloaded to the browser's APIs, and its callback is queued in the task queue. Once the call stack is empty, the event loop picks up the callback, and its execution is prioritized.
- Synchronous logging occurs immediately in the call stack, while the asynchronous API call is offloaded to the browser's APIs. The event loop ensures the callback is queued and executed once the call stack is empty, allowing non-blocking behavior.
- The JavaScript program executes synchronous logging first, and then the asynchronous API call is delegated to the browser's APIs. The event loop monitors the call stack and task queue, ensuring the asynchronous callback is prioritized for execution.
- The event loop manages the asynchronous API call, queuing its callback, and ensuring it is executed once the call stack is empty. Synchronous logging happens directly in the call stack, maintaining a smooth flow of execution in the JavaScript program.
The flow of execution in a JavaScript program involves synchronous logging and asynchronous API calls. The synchronous code is executed first, followed by the asynchronous API call, which is offloaded to the browser's APIs. The event loop ensures that the callback is queued and prioritized for execution once the call stack is empty. Understanding this flow is essential for handling mixed synchronous and asynchronous operations effectively.
Using _________, you can condense an array into a single value, optionally starting with an initial value.
- map
- reduce
- filter
- forEach
The correct answer is reduce. This method allows you to condense the elements of an array into a single value, using a provided function. It is particularly useful for tasks like summing values or finding the maximum element.
Asynchronous callbacks are placed in a queue known as the __________ queue.
- Callback Queue
- Event Queue
- Promise Queue
- Execution Queue
Asynchronous callbacks are placed in the Callback Queue, and they wait for the Event Loop to move them to the Call Stack for execution when the stack is empty.
Is it possible to destructure properties from nested objects?
- Yes
- No
- Only if the nested object has a single property
- Only if the nested object is declared as a constant
Yes, in ES6, destructuring assignment can be used to extract properties from nested objects. This allows for a more convenient and concise way of accessing values within nested structures, enhancing code simplicity.
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.
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.