ECMAScript 5 (2009)

• Strict Mode ('use strict'): Enforces better coding practices.
• Array Methods: forEach, map, filter, reduce, some, every.
• Object Methods: Object.keys(), Object.create().
• Getter/Setter Properties: Define computed properties.
• JSON Support: JSON.parse(), JSON.stringify().
• bind() Method: Binds this to a function.
• Property Descriptors: Control property attributes like writable, configurable.

ECMAScript 6 (ES6) - 2015

• let and const: Block-scoped variables.
• Arrow Functions (=>): Shorter syntax for functions.
• Template Literals: String interpolation using backticks.
• Default Parameters: Function parameters with default values.
• Destructuring: Extract values from objects/arrays.
• Spread (...) and Rest Parameters: Expanding and collecting values.
• Classes (class): Syntactic sugar over constructor functions.
• Modules (import / export): Native module support.
• Promises: Handle asynchronous operations.
• Map and Set: New data structures.
• Generators (function*): Pause and resume execution.

ECMAScript 7 (ES7) - 2016

• Exponentiation Operator (**): 2 ** 3 === 8.
• Array.prototype.includes(): Check if an array contains a value.

ECMAScript 8 (ES8) - 2017

• Async/Await: Simplifies working with Promises.
• Object Entries and Values: Object.entries(), Object.values().
• String Padding: padStart(), padEnd().
• Trailing Commas in Function Parameters: Avoid syntax errors in version control.
• Shared Memory & Atomics: Multi-threaded JS via SharedArrayBuffer.

ECMAScript 9 (ES9) - 2018

• Rest/Spread in Objects: { ...obj }.
• Promise.prototype.finally(): Runs after a Promise resolves/rejects.
• Asynchronous Iteration (for await...of): Async iterators.

ECMAScript 10 (ES10) - 2019

• Array.prototype.flat() & flatMap(): Flatten nested arrays.
• Object.fromEntries(): Convert key-value pairs into objects.
• Optional Catch Binding: catch { } without explicitly defining an error variable.
• String Trim Methods: trimStart(), trimEnd().
• Symbol Description: Symbol('desc').description.

ECMAScript 11 (ES11) - 2020

• BigInt (123n): Large integer support.
• Dynamic import(): Asynchronous module loading.
• Nullish Coalescing (??): x = a ?? 'default'.
• Optional Chaining (?.): Safe property access.
• Promise.allSettled(): Resolves after all Promises settle.
• String matchAll(): Returns all matches in a string.
• Global This (globalThis): Unified global object access.

ECMAScript 12 (ES12) - 2021

• Numeric Separators (1_000_000): Improves readability.
• replaceAll(): Replace all instances in a string.
• WeakRefs & FinalizationRegistry: Manage memory manually.
• Logical Assignment (&&=, ||=, ??=): Shorter conditional assignments.

ECMAScript 13 (ES13) - 2022

• at() Method: Access array elements via negative indices.
• Object.hasOwn(): Better alternative to hasOwnProperty.
• Class Private Fields & Methods: #privateField.
• Top-Level await: await outside async functions.

ECMAScript 14 (ES14) - 2023

• Array findLast() & findLastIndex(): Find last matching element.
• Set Methods: union(), intersection(), difference(), symmetricDifference().
• Hashbang (#!) in Scripts: Support for Unix-style shebangs.
• Symbols as WeakMap Keys: Improved memory handling.

Upcoming Features (ESNext)

• Explicit Resource Management (using): Auto-dispose resources.
• Temporal API: Improved date/time handling.
• Pipeline Operator (|>): Streamline function chaining.

Frequently Asked Questions (FAQ)

What are the most important features introduced in ES6?

ES6 (ECMAScript 2015) introduced several major features, including let and const for block-scoped variables, arrow functions for shorter syntax, classes, template literals, destructuring, promises for asynchronous programming, and native modules.

How does async/await improve JavaScript?

Introduced in ES8 (2017), async/await simplifies working with Promises by allowing developers to write asynchronous code that looks and behaves like synchronous code, making it much easier to read and maintain.

What is ESNext in JavaScript?

ESNext is a dynamic term that refers to the next upcoming version of the ECMAScript standard. It encompasses proposals that are currently being evaluated and implemented by browser vendors before becoming officially integrated.