If you have a Symbol mySymbol, you can access its description using mySymbol.__________.
- name
- description
- valueOf
- toString
The correct property to access the description of a Symbol is description. The description property is used to get or set the description of a Symbol, providing additional information about the Symbol.
When a generator function is initially called, it returns a(n) __________ object.
- Generator
- Promise
- Iterator
- Iterable
When a generator function is called, it returns an iterator object. This object can be used to iterate through the values generated by the generator using the next() method. The other options do not represent the initial return type of a generator function.
How does ES6 support dynamic property names in object literals?
- Computed Property Names
- Object Linking
- Dynamic Key Binding
- Property Aliasing
ES6 supports dynamic property names through computed property names. By using square brackets around an expression within an object literal, you can create properties with names determined at runtime. This enhances the flexibility and expressiveness of object literals.
ES6 enables deeper recursion without a stack overflow by using _________ tail calls.
- Deferred
- Optimized
- Asynchronous
- Tail
In-depth content in the explanation. ES6 introduces the concept of tail call optimization, allowing for deeper recursion without causing a stack overflow. Tail calls occur when a function's last action is a recursive call, and ES6 optimizes these tail calls to prevent excessive stack usage.
To access a parent class's method in a child class, the __________ keyword is used inside the method.
- super
- this
- parent
- extends
In JavaScript, the super keyword is used to refer to the parent class. When used inside a method in a child class, it allows you to call the corresponding method in the parent class. This is particularly useful for accessing and invoking the parent class's method from within the child class.
In terms of scope, how do variables and functions behave differently in ES6 Modules compared to CommonJS modules?
- Variables and functions have block scope
- Variables have block scope, functions have global scope
- Variables and functions have global scope
- Variables have global scope, functions have block scope
ES6 Modules introduce block scope for both variables and functions, offering better encapsulation. In contrast, CommonJS has function-level scope for variables and global scope for functions, leading to potential issues with variable leakage.
If a module exports several named items, how can you import all of them at once?
- import * as allExports from 'module';
- import { export1, export2 } from 'module';
- import allExports from 'module';
- import { * } from 'module';
To import all named exports from a module at once, you use the syntax import * as allExports from 'module';. This creates an object containing all the exports, and you can access them using dot notation, e.g., allExports.exportName.
What is a key difference between a Map and a WeakMap in JavaScript?
- Both can store key-value pairs, but the keys in WeakMap must be objects, and they don't prevent the objects from being garbage collected.
- Maps allow any data type as keys, while WeakMaps only allow objects as keys.
- Maps are iterable, while WeakMaps are not iterable.
- WeakMaps have a getKeys method to retrieve all keys.
Maps are versatile and allow various data types as keys, while WeakMaps are designed for enhanced privacy, with keys limited to objects and no direct method for key retrieval.
In a node.js application, how would you handle errors when performing multiple asynchronous operations in parallel?
- Implementing a try-catch block around each asynchronous operation
- Utilizing the Promise.all() method with a single catch block for error handling
- Using multiple catch blocks for each asynchronous operation
- Handling errors outside the asynchronous operations entirely
In the scenario of multiple asynchronous operations, using Promise.all() simplifies error handling by allowing a single catch block to capture errors from any of the parallel operations. This promotes cleaner and more concise error management, making it easier to identify and address issues in the asynchronous flow. Multiple catch blocks might lead to redundancy and make the code harder to maintain.
In the context of tree shaking, what is the significance of the "sideEffects" flag in a package.json file?
- Specifies files that should be excluded from the tree-shaking process
- Indicates whether the package has side effects that prevent tree shaking
- Determines the priority of modules during tree shaking
- Flags external dependencies for tree shaking
The "sideEffects" flag in package.json is used to inform the bundler about the side effects of a module. If set to false, it allows the bundler to perform aggressive tree shaking by eliminating unused exports. If set to true, it implies the module has side effects, and the bundler avoids tree shaking to maintain those side effects.