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const
A keyword used to declare block-scoped, read-only variables in JavaScript.
What is the purpose of Arrow functions in JavaScript?
Arrow functions provide a concise syntax for writing functions and lexically bind the this value, making them useful for callbacks.
Template Literals
String literals that allow embedded expressions, using backticks (`) and placeholders with ${expression}` syntax.
What is a Promise in JavaScript?
An object representing the eventual completion or failure of an asynchronous operation, allowing chaining with .then() and .catch() methods.
Destructuring Assignment
A syntax that allows unpacking values from arrays or properties from objects into distinct variables.
Spread Operator
An operator (...) that expands an iterable (like an array) into individual elements.
Rest Parameters
A syntax that allows a function to accept an indefinite number of arguments as an array, using the ... prefix.
What is the difference between var, let, and const?
var is function-scoped or globally-scoped, let and const are block-scoped. const cannot be reassigned.
What are default parameters in JavaScript?
Parameters that allow named parameters to be initialized with default values if no value or undefined is passed.
Symbol
A unique and immutable primitive value used as an identifier for object properties.
WeakMap
A collection of key-value pairs where keys are objects and values can be collected by garbage collection if there are no other references.
WeakSet
A collection of unique objects, similar to a Set, but where objects are held weakly and can be garbage collected.
What is async/await in JavaScript?
async/await is syntactic sugar for working with promises, making asynchronous code look and behave like synchronous code.
Modules
A feature in ES6 that allows code to be organized into separate files and imported/exported using import and export statements.
What is Promise.all()?
A method that takes an iterable of promises and returns a single promise that resolves when all of the promises have resolved.
What is Promise.race()?
A method that returns a promise that resolves or rejects as soon as one of the promises in the iterable resolves or rejects.
What is Promise.finally()?
A method that allows you to execute code regardless of whether the promise was resolved or rejected.
What is the Reflect API?
An API that provides methods for interceptable JavaScript operations, mirroring those of the Proxy handler methods.
Proxy
An object that wraps another object or function and intercepts operations like property lookup and assignment.
What is the purpose of Generators in JavaScript?
Generators are functions that can be paused and resumed, allowing for asynchronous programming and handling of sequences.
What is a Tagged Template Literal?
A template literal preceded by a function, allowing custom processing of the template's content.
Iterators
An object that enables traversal over elements of a collection, returning each value via the next() method.
What is a for...of loop?
A loop construct that iterates over iterable objects like arrays, strings, and Map/Set objects.
What does the Array.from() method do?
It creates a new array instance from an array-like or iterable object.
What does the Array.of() method do?
It creates a new array instance with a variable number of arguments, regardless of number or type of the arguments.
What is a Class in JavaScript?
A blueprint for creating objects with predefined properties and methods, introduced in ES6.
What is super in JavaScript?
A keyword used to access and call functions on an object's parent.
Static Methods
Methods defined on the class itself, rather than on instances of the class.
What is Object.assign() used for?
It copies the values of all enumerable own properties from one or more source objects to a target object.
What does Object.entries() return?
An array of a given object's own enumerable property [key, value] pairs.
What does Object.values() return?
An array of a given object's own enumerable property values.
What is Array.prototype.includes()?
A method that determines whether an array includes a certain value, returning true or false.
What is the purpose of the Reflect API in JavaScript?
To provide a set of static methods to perform operations on objects that are usually done directly, mirroring the methods of Proxy handlers.
What is an Async Iterator in JavaScript?
An object implementing the AsyncIterable protocol, allowing asynchronous iteration with for await...of loops.
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