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.
Can you nest template literals within each other?
- Yes
- No
- Only if they have the same variables
- Only in arrow functions
Template literals can be nested within each other, allowing for more complex string constructions. This nesting can be useful when building strings that involve multiple layers of dynamic content.
When creating a utility class with common helper functions, how would you ensure that these methods are accessible without instantiating the class?
- Use static methods
- Use private methods
- Use public methods
- Use protected methods
In ES6, you can ensure that methods in a utility class are accessible without instantiating the class by defining them as static methods. Static methods are associated with the class itself rather than instances, allowing you to call them directly on the class without creating an object. This is beneficial for utility classes where instantiation is unnecessary, and you want to organize related functions.
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.
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.
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 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.
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.
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.
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 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.
Does a function that reads external files qualify as a pure function?
- Yes, as long as it only reads and does not modify
- No, any file reading operation is impure
- Only if it's a text file
- Only if it's a small file
No, reading external files is considered a side effect, and pure functions should not have side effects. Pure functions should only operate on their input parameters and not rely on external factors such as file systems or databases.