The ES6 Module system supports __________ import syntax, which is not possible in CommonJS.
- Dynamic
- Static
- Deferred
- Asynchronous
ES6 introduced static import syntax for modules, allowing developers to specify exactly what they want to import. This is not possible in CommonJS, where imports are dynamic and are resolved at runtime.
Imagine you're developing a real-time voting system, where each user can only vote once but you need to efficiently check if a user has already voted. What ES6 data structure would you implement for storing user IDs?
- Map
- Set
- WeakMap
- WeakSet
For a real-time voting system, a Set would be the best choice. A Set only allows unique values, making it efficient for storing user IDs and quickly checking if a user has already voted, ensuring each user can only vote once in the system.
When using super in a constructor, it initializes the _______ of the derived class.
- Properties
- Constructor
- State
- Methods
In a derived class constructor, super initializes the properties of the derived class, calling the constructor of the parent class. This sets up the state for the derived class.
What is a key feature of arrow functions regarding the handling of the this keyword?
- They bind the this keyword dynamically
- They do not have access to the this keyword
- They always refer to the this of the global object
- They bind the this keyword statically
Arrow functions do not have their own this context; instead, they inherit the this value from the surrounding lexical scope. This is a crucial feature that can prevent the common issue of losing the correct this context in nested functions.
What is a higher-order function in JavaScript?
- A function that takes another function as an argument.
- A function that operates on other functions, either by taking them as arguments or by returning them.
- A function that only performs operations on numbers.
- A function that can only be called once.
In JavaScript, a higher-order function is one that either takes a function as an argument or returns a function. This allows for the creation of more flexible and reusable code.
To insert a variable into a template literal, use the ${} __________.
- Parentheses ()
- Curly braces {}
- Square brackets []
- Angle brackets <>
To insert a variable into a template literal, use the ${} syntax with curly braces. This allows for dynamic content within the string, making it more flexible and readable.
Static methods are often used for _________ that are relevant to all instances of a class.
- Properties
- Functionality
- Events
- Callbacks
In object-oriented programming, static methods are associated with a class rather than instances. They are often used for functionality that is relevant to all instances of a class, rather than a specific instance. This helps in organizing code and improving code readability.
How does the Symbol type interact with the Object.getOwnPropertySymbols() method?
- It returns an array of all symbol properties found directly upon the given object.
- It throws an error since symbols are not enumerable.
- It returns an object containing all symbol properties found directly upon the given object.
- It only returns symbols with specific descriptors.
The Object.getOwnPropertySymbols() method returns an array of all symbol properties found directly upon the given object, regardless of their enumerability. It allows you to access symbols that are not enumerable in regular object iteration.
The _________ pattern in ES6 is a design pattern used to compose objects from small reusable components.
- Factory
- Composite
- Mixin
- Observer
The correct option is Mixin. In ES6, the Mixin pattern involves composing objects by combining small, reusable components. This allows for better code organization and reusability. Mixins are a way to enhance a class with the methods of another class without the need for inheritance.
Can you access instance properties from a static method?
- Yes, using the this keyword.
- No, it results in a runtime error.
- Yes, using the super keyword.
- No, instance properties are inaccessible.
No, you cannot access instance properties directly from a static method. Static methods are associated with the class itself and do not have access to instance-specific data. Option D is correct.