Consider a library with multiple utility functions; how would you structure the exports to optimize for tree shaking?
- export function util1() {} export function util2() {}
- export { util1, util2 }
- export default { util1, util2 }
- export const util1 = () => {}; export const util2 = () => {};
To optimize for tree shaking, individually exporting functions (export function util1() {}) allows dead code elimination, ensuring only the used functions are included in the final bundle.
In object methods, using arrow functions can lead to issues when relying on the this keyword, as it does not bind its own this, but inherits it from the ________ scope.
- Parent
- Global
- Lexical
- Block
Arrow functions inherit the this value from their lexical scope, which means the scope in which they were defined. This can lead to unexpected behavior when used in object methods.
The spread operator can be used in ES6 to clone an array without ________ the original array.
- Modifying
- Changing
- Altering
- Mutating
The spread operator can be used to clone an array without mutating the original array. It creates a shallow copy, meaning nested objects are still references, but the outer array is a new instance.
If a default parameter references another parameter, what order must they be declared in?
- After the parameter it references
- Before the parameter it references
- It doesn't matter
- They must be declared in a separate function
In JavaScript, default parameters are evaluated at the time of the function call. Explanation should cover the order of declaration and how the referencing works.
The super keyword in static methods refers to the _______ class's static methods and properties.
- Parent
- Child
- Sibling
- Derived
In a static method, super refers to the parent class's static context. This is useful for accessing static methods or properties of the parent class.
To execute multiple async functions in parallel and wait for all of them, use __________.
- Promise.all()
- Promise.race()
- Promise.parallel()
- Promise.sequence()
To execute multiple asynchronous functions concurrently and wait for all of them to complete, the appropriate method is Promise.all(). It takes an array of promises and resolves when all the promises in the array have resolved. Promise.race() would resolve as soon as any of the promises in the array resolves, which might not be suitable for waiting for all of them. Understanding the correct usage of Promise.all() is crucial for efficient handling of parallel asynchronous tasks.
How does the static structure of ES6 Modules aid in tree shaking compared to CommonJS?
- Easier debugging due to explicit dependencies
- Improved dead code elimination
- Faster runtime performance
- Better support for dynamic imports
ES6 Modules have a static structure, allowing tools to analyze dependencies at build time. Tree shaking is the process of eliminating dead code, and ES6 Modules excel in this regard, making it easier to eliminate unused code during bundling.
In ES6, how does the shorthand for method properties affect the 'function' keyword in object literals?
- It removes the need for the 'function' keyword.
- It enforces the use of the 'function' keyword.
- It modifies the behavior of the 'function' keyword.
- It's not related to the 'function' keyword.
In ES6, the shorthand for method properties allows omitting the 'function' keyword when defining methods in object literals. It enhances code readability by providing a more concise syntax for method definitions within objects. This syntactic sugar simplifies the declaration of methods in objects, making the code cleaner and more modern.
The concept of ________ is essential in understanding how functions are combined in functional composition.
- Closure
- Immutability
- Prototypes
- Referential transparency
The concept of referential transparency is essential in understanding how functions are combined in functional composition. Referential transparency means that a function, given the same inputs, will always return the same output, allowing for easier reasoning about the behavior of composed functions.
When using const to declare a variable, what type of assignment is mandatory?
- Reassignment
- Initialization
- Increment
- Declaration
When you declare a variable with const, you must initialize it with a value. const variables cannot be declared without an initial value, and they cannot be reassigned to a different value after initialization.