Which method is essential for an object to be an iterator?
- next() method
- getIterator() method
- iterate() method
- forEach() method
An iterator in JavaScript must implement the next() method. This method is called on each iteration and should return an object with properties like value and done, indicating the next value in the sequence and whether the iteration is complete.
How do dynamic imports interact with tree shaking in modern JavaScript bundlers?
- Enhances tree shaking
- Impedes tree shaking
- No interaction
- Works only in development mode
Dynamic imports enhance tree shaking by enabling the removal of unused code during the bundling process. Tree shaking is more effective as it can analyze the dynamic imports and eliminate dead code paths, leading to smaller bundle sizes.
The String.raw tag function returns a string where escape sequences like n are treated as _______ text.
- Formatted
- Raw
- Escaped
- Plain
The String.raw tag function in ES6 returns a string where escape sequences are treated as raw text. It is useful when you want to include backslashes in a string without interpreting them as escape characters.
The ES6 Module system supports __________ import syntax, which is not possible in CommonJS.
- Dynamic
- Static
- Deferred
- Asynchronous
ES6 introduced static import syntax for modules, allowing developers to specify exactly what they want to import. This is not possible in CommonJS, where imports are dynamic and are resolved at runtime.
Imagine you're developing a real-time voting system, where each user can only vote once but you need to efficiently check if a user has already voted. What ES6 data structure would you implement for storing user IDs?
- Map
- Set
- WeakMap
- WeakSet
For a real-time voting system, a Set would be the best choice. A Set only allows unique values, making it efficient for storing user IDs and quickly checking if a user has already voted, ensuring each user can only vote once in the system.
When using super in a constructor, it initializes the _______ of the derived class.
- Properties
- Constructor
- State
- Methods
In a derived class constructor, super initializes the properties of the derived class, calling the constructor of the parent class. This sets up the state for the derived class.
What is a key feature of arrow functions regarding the handling of the this keyword?
- They bind the this keyword dynamically
- They do not have access to the this keyword
- They always refer to the this of the global object
- They bind the this keyword statically
Arrow functions do not have their own this context; instead, they inherit the this value from the surrounding lexical scope. This is a crucial feature that can prevent the common issue of losing the correct this context in nested functions.
What is a higher-order function in JavaScript?
- A function that takes another function as an argument.
- A function that operates on other functions, either by taking them as arguments or by returning them.
- A function that only performs operations on numbers.
- A function that can only be called once.
In JavaScript, a higher-order function is one that either takes a function as an argument or returns a function. This allows for the creation of more flexible and reusable code.
To insert a variable into a template literal, use the ${} __________.
- Parentheses ()
- Curly braces {}
- Square brackets []
- Angle brackets <>
To insert a variable into a template literal, use the ${} syntax with curly braces. This allows for dynamic content within the string, making it more flexible and readable.
Static methods are often used for _________ that are relevant to all instances of a class.
- Properties
- Functionality
- Events
- Callbacks
In object-oriented programming, static methods are associated with a class rather than instances. They are often used for functionality that is relevant to all instances of a class, rather than a specific instance. This helps in organizing code and improving code readability.