The "sideEffects" property in package.json helps tree shaking by indicating if a module may contain _______.
- Side Effects
- Pure Functions
- Impure Functions
- Async Functions
The correct option is (b) Pure Functions. The "sideEffects" property, when set to false, informs the module bundler that the module does not have side effects, making it eligible for tree shaking. Pure functions are side effect-free functions that only depend on their input parameters, making them suitable for elimination during tree shaking.
What happens if you try to redeclare a variable declared with let in the same scope?
- It generates an error
- It assigns a new value to the variable
- It creates a new variable with the same name
- It deletes the variable
When you attempt to redeclare a variable with let in the same scope, it will generate an error. This is because variables declared with let cannot be redeclared in the same scope.
In what way does the super keyword facilitate inheritance in ES6 classes?
- It allows access to the parent class's methods and properties
- It creates an instance of the parent class
- It prevents the child class from inheriting certain methods
- It is used to instantiate the parent class
The super keyword in ES6 classes is used to access the methods and properties of the parent class. It is commonly used in the constructor of the child class to call the constructor of the parent class and initialize the inherited properties.
How does the lack of enumeration in WeakMap and WeakSet impact their use cases?
- Lack of enumeration in WeakMap and WeakSet prevents direct access to their elements.
- Enumeration is not essential in WeakMap and WeakSet, as they are designed for scenarios where enumeration is not needed.
- Lack of enumeration provides an added layer of security, making it difficult for external code to access the internal state of these structures.
- Enumeration is not relevant in the context of WeakMap and WeakSet, as their primary use is for memory management.
Lack of enumeration allows these structures to be more suitable for scenarios where privacy and encapsulation are critical.
When optimizing a web application for performance, considering the need for tree shaking and module caching, which module system offers more advantages?
- ES6 Modules
- CommonJS
- Both have similar performance optimizations
- Depends on the specific use case
ES6 Modules provide better support for tree shaking, a process that eliminates unused code during the build, resulting in smaller bundles and improved performance. Additionally, ES6 Modules support native module caching, further enhancing performance by reducing redundant module loading.
In a situation where a web application needs to fetch data from an API and handle both the data response and possible errors, what are the best practices using Promises?
- Using async/await
- Promise.catch
- Using try/catch
- Using setTimeout
The best practice in handling both successful data responses and errors with Promises is by using async/await. This allows for cleaner and more readable code, making it easier to handle both resolved and rejected promises in a structured and organized manner.
How does the Promise.all method interact with async/await?
- Waits for all promises to resolve and then proceeds
- Rejects if any of the promises reject
- Executes promises concurrently
- Resolves immediately without waiting
Promise.all waits for all promises to resolve successfully before proceeding. If any of the promises reject, the entire Promise.all rejects. This makes it useful when you have multiple asynchronous operations that can be executed concurrently and you want to wait for all of them to complete. When combined with async/await, you can use it to await multiple asynchronous operations concurrently.
How do you create a new object that inherits from an existing object in ES6?
- Object.create()
- Object.inherit()
- Object.extend()
- Object.instantiate()
In ES6, the Object.create() method is used to create a new object that inherits from an existing object. It sets up prototype chaining, allowing the new object to inherit properties and methods from the existing one.
Can a generator function yield another generator function? If so, how is it achieved?
- No, it is not possible
- Yes, using yield* keyword
- Yes, using async keyword
- Yes, using yield keyword
Yes, a generator function can yield another generator function using the yield* keyword. This allows for the delegation of the generator control, enabling the composed use of generators within generators. This feature enhances the modularity and reusability of generator functions.
How does a pure function handle dependencies or external variables?
- Manages dependencies internally
- Avoids external dependencies
- Handles dependencies through callbacks
- Utilizes global variables
In a pure function, dependencies are avoided to maintain purity. External variables could introduce side effects, violating the principle of purity.