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.
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.
If a project is using a third-party library with multiple components, but only a few are needed, how can tree shaking be utilized for efficiency?
- Import only the needed components from the library in the code.
- Include the entire library as is.
- Manually remove unused components from the library.
- Use a separate smaller library for the required components.
Tree shaking can be leveraged by importing only the necessary components from the third-party library. This way, the bundler can exclude the unused parts during the build process, optimizing the bundle size. The other options are not efficient for tree shaking purposes.
When you need to execute a function on an array and need the result to be a single output value, use _________.
- map
- forEach
- reduce
- filter
The reduce method is used to execute a reducer function on each element of the array, resulting in a single output value.
Dynamic imports are especially useful for __________ loading of modules.
- Asynchronous
- Synchronous
- Sequential
- Parallel
Dynamic imports are especially useful for asynchronous loading of modules. Unlike traditional synchronous imports, dynamic imports allow modules to be loaded asynchronously, enabling the application to continue executing code without waiting for the module to be fully loaded. This asynchronous behavior is beneficial for optimizing performance, especially in scenarios where certain modules are only needed under specific conditions. Understanding the advantages of asynchronous module loading is crucial for developing efficient and responsive JavaScript applications.