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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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