To re-export all named exports from a module, use export * from _________.
- export * from 'moduleName';
- export all from 'moduleName';
- export {all} from 'moduleName';
- export named from 'moduleName';
To re-export all named exports from a module in ES6, you use the export * from 'moduleName'; syntax. This allows you to export all the named exports from one module to another without listing them individually.
Q1: Imagine you are creating a caching mechanism for a web application. Would you choose a WeakMap or a Map for storing cached data and why?
- WeakMap
- Map
- Both WeakMap and Map
- Neither WeakMap nor Map
In a caching mechanism, using a WeakMap is preferred over a Map. This is because a WeakMap allows the keys to be garbage collected if there are no other references to them, which is beneficial for caching scenarios where you want the cached data to be automatically cleared when the corresponding objects are no longer in use. A Map, on the other hand, would retain the keys even if they are not needed anymore, leading to potential memory leaks in a caching context.
How does the call stack in JavaScript relate to the concept of 'blocking'?
- It represents the order of function calls
- It handles asynchronous tasks
- It causes delays in code execution
- It manages the memory allocation
The call stack in JavaScript tracks the execution of functions. When a function is called, it's added to the stack, and when it returns, it's removed. Blocking occurs when a function takes a long time to execute, causing subsequent code to wait. Understanding this helps optimize code for performance.
The Array method __________ is an example of a higher-order function that takes a function as its argument.
- Map
- Filter
- Reduce
- Concat
The reduce method in JavaScript arrays is a higher-order function that takes a callback function to accumulate the elements of an array into a single result. It is commonly used for tasks like summing or product accumulation.
When implementing a module that provides extension hooks, how can Symbols be used to create non-conflicting method names?
- Using generic function names
- Using Symbols as method names
- Using random strings as method names
- Using module-specific prefixes
The correct option is using Symbols as method names. Symbols allow you to create non-conflicting method names by using them as keys for object properties. This is particularly useful in the context of module extension hooks, where different modules can use Symbols without risking naming conflicts. Generic function names, random strings, and module-specific prefixes may lead to conflicts, making Symbols a more suitable choice for this scenario.
Object literals in ES6 can include __________, a shorthand for defining functions.
- Arrow Functions
- Prototypes
- Generators
- Callbacks
ES6 introduced arrow functions as a shorthand for defining functions within object literals, offering a more concise syntax and lexically scoped 'this'.
What happens when you use the return keyword in a single-line arrow function?
- The function returns undefined
- The function returns the value after the arrow
- The function throws an error
- The function returns an array
In arrow functions, if the body is a single expression, it is implicitly returned. So, using the return keyword is optional. Option B is correct.
__________ can be used to execute a callback on every element in the array, creating a new array with the results.
- map
- forEach
- reduce
- filter
The forEach method can be used to execute a callback function on each element of an array. However, it doesn't create a new array with the results.
Generator functions can be used to implement _________ programming patterns, like handling asynchronous operations in a synchronous manner.
- Synchronous
- Asynchronous
- Parallel
- Concurrent
Generator functions in JavaScript can be used to implement asynchronous programming patterns. By yielding promises and using async/await syntax, asynchronous operations can be handled in a more synchronous-looking manner, enhancing code readability and maintainability.
What is the benefit of using tree shaking with ES6 modules?
- Eliminates dead code and reduces bundle size
- Improves module readability and organization
- Enhances runtime performance through JIT compilation
- Enables better debugging with source maps
Tree shaking is a technique in which unused or dead code is eliminated during the bundling process. It helps reduce the final bundle size, resulting in faster loading times and improved performance.