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.
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.
What happens if you try to import a named export that doesn't exist in the module?
- It will result in a runtime error.
- It will import a null value.
- It will import an undefined value.
- It will not have any effect, and the code will run without errors.
If you try to import a named export that doesn't exist in the module, it will result in a runtime error. The import statement expects the named export to exist, and an attempt to import a non-existent export will throw an error.
To dynamically import a module based on a variable, the variable's value is included inside the __________.
- Template Literal
- Parentheses
- Square Brackets
- Curly Braces
To dynamically import a module based on a variable, the variable's value is included inside the square brackets of the import statement. This feature is known as dynamic import expressions, allowing developers to specify the module path at runtime. By using square brackets, the JavaScript interpreter treats the import statement as a dynamic expression, enabling more flexibility in module loading. Understanding this syntax is essential for dynamically loading modules based on runtime conditions, enhancing the adaptability of the application.
Can you use const within a for...of loop to declare a variable for each iteration?
- Yes
- No
- It depends
- Not applicable
In a for...of loop, the variable declared using const cannot be reassigned in each iteration. The loop variable retains its value throughout the loop, making it unsuitable for situations where reassignment is needed for each iteration.