If you're building a library with a primary functionality and several auxiliary functions, how would you organize your exports?
- Using named exports for each auxiliary function
- Using a default export for the primary functionality and named exports for auxiliary functions
- Using a default export for each function, combining primary and auxiliary functionalities
- Using a single named export for the entire library
When building a library, using a default export for the main functionality and named exports for auxiliary functions is a common practice. This way, consumers can import only the specific functionalities they need, optimizing bundle size and avoiding unnecessary code.
In a WeakMap, keys must be of type _________, and they are not enumerable.
- Object
- String
- Symbol
- Number
In a WeakMap, keys must be of type Symbol, and they are not enumerable. Symbols are unique and help in creating private properties or methods. Using other types as keys will result in unexpected behavior.
How would you use mixins in ES6 to enhance classes in a library, without modifying the original source code?
- By directly modifying the source code of the original class.
- By creating a new class that extends the original class and includes the desired mixins.
- By using decorators to dynamically apply mixins to the original class.
- By creating a higher-order function that adds mixins to the original class prototype.
To enhance classes in a library without modifying the source code, you can create a new class that extends the original class and includes the desired mixins. This follows the concept of class extension and composition.
What happens if super() is called multiple times in a constructor?
- It triggers an error
- It executes the parent constructor multiple times
- Only the last call is effective
- It has no effect
Calling super() multiple times in a constructor is an error. It must be called once and must be the first statement in the constructor. Subsequent calls to super() would result in an error.
What types of values can be added to a WeakSet?
- Only objects can be added.
- Any data type, including primitives, can be added.
- Only functions can be added.
- Only arrays can be added.
WeakSets exclusively allow objects, emphasizing their use for storing unique object references and aiding in scenarios like memory management.
Can a pure function modify a global variable?
- Yes
- No
- It depends
- Only if it's a constant variable
No, a pure function should not modify global variables or any external state. It should only depend on its input parameters to produce the output and should not have side effects. Modifying global variables violates the principles of pure functions.
In a web application, how can higher-order functions be used to enhance event handling?
- reduce
- map
- forEach
- filter
The correct option is forEach. forEach is commonly used for iterating over elements in an array, making it suitable for enhancing event handling in a web application where actions need to be performed on each element.
What is the main purpose of default parameters in ES6 functions?
- Enhancing Function Flexibility
- Enabling Type Annotations
- Facilitating Function Overloading
- Simplifying Function Parameter Handling
Default parameters in ES6 functions provide a way to set default values for function parameters, enhancing flexibility by allowing functions to be called with fewer arguments or without any arguments. This can simplify code and handle different use cases without requiring explicit checks for undefined values.
The _________ method is used to execute a function on each item in a Set.
- forEach
- execute
- loop
- iterate
The correct method is forEach. The forEach method in Set allows you to execute a provided function once for each element in the Set, in insertion order. Example: mySet.forEach((value) => console.log(value));.
Using a WeakMap for private data ensures that the data is garbage collected when the object key is no longer ________.
- Referenced
- Immutable
- Mutable
- Valid
When using a WeakMap for private data, the data is tied to the object key, and it will be garbage collected when the object is no longer referenced elsewhere in the code. This helps in managing memory efficiently for private data in JavaScript.