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.
What is a mixin in the context of JavaScript ES6?
- A way to create variables in ES6
- A function that takes two objects and returns a new object
- A method for adding properties and methods to a class
- A type of loop in ES6
In JavaScript ES6, a mixin is a way to compose classes by adding properties and methods to a class. It allows the reuse of functionalities and promotes code reusability. Unlike inheritance, mixins do not rely on a hierarchical relationship between classes. They enhance the flexibility and maintainability of code.
How do default parameters interact with destructuring assignment in function arguments?
- They can't be used together
- Destructuring assignment takes precedence
- The function ignores the default parameters
- Destructuring is not supported in ES6
Default parameters and destructuring can be used together, and destructuring takes precedence. Explanation should elaborate on how they work together.
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.
How does the rest operator differ from the spread operator in its syntax?
- It uses the same syntax as the spread operator
- It uses the same syntax as the spread operator but with an extra parameter
- It uses a different syntax with three dots (...)
- It doesn't exist in ES6
The rest operator also uses three dots (...) but in a different context. It is used to represent an indefinite number of arguments as an array in function parameters, providing a more concise syntax for working with variadic functions.
What is a common way to handle errors in async/await functions?
- try...except
- errorHandling
- catch
- handleError
In async/await functions, the common way to handle errors is by using the try...catch block. This allows you to wrap the asynchronous code within the try block and catch any errors that may occur during its execution. The catch block is then used to handle and respond to those errors.
Can a Symbol be used as an index in an Array?
- Yes, symbols can be used as array indices without any restrictions.
- No, symbols cannot be used as indices in an array.
- Yes, but with some limitations and considerations.
- Only if the symbol is explicitly converted to a string.
Symbols cannot be used as array indices directly. They are not automatically converted to strings, and using them as indices will not work as expected.
Functions that perform HTTP requests are not considered pure because they _________.
- Use Arrow Functions
- Have Side Effects
- Are Asynchronous
- Are Synchronous
Functions that perform HTTP requests are not considered pure because they have side effects. Purity in functions means that they do not cause any observable side effects, and HTTP requests involve external actions that can impact the program's state.
When a const variable is declared in a block scope, what is the scope of this variable?
- Local to the block
- Global
- Function-level
- Lexical scope
In JavaScript, when you declare a constant variable (const) inside a block (like an if statement or a loop), the scope of that variable is limited to the block. This means it cannot be accessed outside of that block.