When you extend a class in ES6, what must you do before using this in the constructor?
- Initialize the subclass properties
- Call the super() method
- Import the parent class
- Define a new constructor
In ES6, when extending a class, you must call super() in the constructor of the subclass before using this. The super() call initializes the properties of the parent class.
To prevent modifications to an object’s prototype, the _________ method can be used to seal the prototype.
- Freeze
- Seal
- PreventExtensions
- Protect
The seal method in JavaScript can be used to prevent any further addition or deletion of properties on an object, including its prototype. This ensures that the prototype remains fixed and cannot be modified.
How do you access a static property within a class method?
- Using this.propertyName
- Using self.propertyName
- Using the class name followed by a dot and the property name
- Using super.propertyName
To access a static property within a class method, you use the class name followed by a dot and the property name. This is because static properties are associated with the class itself, not with instances, so you reference them through the class name.
To iterate over an array's elements using a for...of loop, write for (const element _______ array).
- in
- of
- from
- within
In JavaScript, the correct syntax for iterating over an array using a for...of loop is for (const element of array). The of keyword is used to loop over the values in an iterable object like an array.
Can async functions be used as constructors for new objects?
- Yes
- No
- Only in specific JavaScript engines
- Only with the use of decorators
No, async functions cannot be used as constructors for new objects. Async functions always return a Promise, and using them with the new keyword will result in a TypeError. Constructors should return objects, not Promises.
In a subclass constructor, the super keyword must be called before accessing _______.
- parent properties
- child properties
- subclass properties
- constructor properties
In a subclass constructor, the super keyword must be called before accessing parent properties. This is because the super keyword refers to the parent class, and it needs to be invoked first to ensure that the parent's properties are properly initialized before accessing them in the subclass.
Imagine designing a class hierarchy for vehicles. How would you use constructors and the super keyword when creating a class for a specific type of vehicle, like a truck?
- Utilize the constructor to initialize specific properties and use super to call the parent class constructor.
- Ignore constructors and super, relying on default values for properties.
- Use only the super keyword without constructors for simplicity.
- Use constructors but avoid the super keyword for vehicle class creation.
In designing a class hierarchy, the constructor is crucial to initialize specific properties of the truck class. The super keyword ensures that the parent class constructor is called, setting up common attributes shared among all vehicles. This promotes code reusability and a clear inheritance structure.
In object destructuring, the rest operator can be used to gather the remaining properties into a new '__________'.
- Object
- Array
- Variable
- Function
In object destructuring, the rest operator (...) is used to collect the remaining properties of an object into a new array. This allows you to extract specific properties while capturing the rest in a convenient variable, often referred to as an array or an object.
Given an API response with nested data structures, how would destructuring assignment simplify data extraction and handling?
- Extracting specific data becomes concise and readable
- Data extraction becomes slower
- Destructuring cannot be used with nested data structures
- Destructuring has no impact on data handling
Destructuring assignment in ES6 allows developers to extract specific values from nested data structures, making the code more concise and readable. By specifying the desired variables in the destructuring pattern, developers can directly access the required data, avoiding verbose syntax and improving code maintainability. This feature simplifies the process of working with complex API responses or nested objects, enhancing overall code efficiency and clarity.
When building a web application that requests user data from an API and simultaneously posts data to another service, how can Promises enhance code readability and flow?
- Chaining Promises
- Callback Functions
- Asynchronous Callbacks
- Nested Callbacks
Promises allow for chaining, which enhances code readability. Chained promises provide a more elegant and sequential way of handling asynchronous operations compared to nested callbacks, making the code more readable and maintainable.