ECMAScript Versions

Quick-reference of notable features added in each ECMAScript edition from ES2015 to ES2026. Listed newest-first. Based on Paweł Grzybek's annual ECMAScript roundup.

ES2026

Feature	Description	Link
Array.fromAsync	Creates an array from an async iterable	MDN
Error.isError	Safe cross-realm error detection	MDN
Math.sumPrecise	Sums an iterable with better floating-point precision	MDN
Uint8Array Base64/hex	Built-in toBase64(), toHex(), fromBase64(), fromHex()	MDN
Iterator.concat	Concatenate multiple iterators into one	MDN
JSON.parse source text access	Reviver gets raw source string; JSON.rawJSON() for lossless BigInts	MDN
Map.prototype.getOrInsert	Insert-if-absent pattern built into Map	MDN

const arr = await Array.fromAsync(asyncGenerator());

const cache = new Map();
const value = cache.getOrInsertComputed("key", () => expensiveCompute());

ES2025

Feature	Description	Link
Set methods	intersection, union, difference, symmetricDifference, isSubsetOf, isSupersetOf, isDisjointFrom	MDN
Iterator Helpers	map, filter, take, drop, flatMap, reduce, toArray on iterators	MDN
Promise.try	Wraps sync or async functions into a Promise chain	MDN
Import Attributes	import x from "./f.json" with { type: "json" }	MDN
Float16Array	Half-precision 16-bit float typed array	MDN
RegExp.escape	Escapes a string for safe use inside a RegExp	MDN
Duplicate named capture groups	Same (?<name>...) allowed in different regex alternatives	MDN
RegExp pattern modifiers	Apply flags like (?i:...) to a sub-expression only	MDN

const a = new Set([1, 2, 3]);
const b = new Set([2, 3, 4]);
a.intersection(b); // Set {2, 3}

const evens = Iterator.from([1, 2, 3, 4, 5])
  .filter(n => n % 2 === 0)
  .toArray(); // [2, 4]

import data from "./config.json" with { type: "json" };

ES2024

Feature	Description	Link
Object.groupBy / Map.groupBy	Group array elements by a callback	MDN
Promise.withResolvers	Returns { promise, resolve, reject } for deferred promises	MDN
Well-Formed Unicode Strings	isWellFormed() and toWellFormed() on strings	MDN
Atomics.waitAsync	Asynchronous atomic wait, usable on the main thread	MDN
RegExp v flag	Unicode set notation with -- subtraction and && intersection	MDN
Resizable ArrayBuffer	ArrayBuffer with maxByteLength and resize()	MDN
ArrayBuffer transfer	transfer() and transferToFixedLength()	MDN

const grouped = Object.groupBy(items, item => item.category);

const { promise, resolve, reject } = Promise.withResolvers();

ES2023

Feature	Description	Link
Change Array by Copy	toReversed(), toSorted(), toSpliced(), with() — immutable operations	MDN
findLast / findLastIndex	Search from the end of an array	MDN
Hashbang Grammar	#!/usr/bin/env node recognized by the parser	MDN
Symbols as WeakMap keys	Non-registered Symbols can be WeakMap/WeakSet keys	MDN

const sorted = arr.toSorted((a, b) => a - b); // original unchanged
const updated = arr.with(2, "new value");

ES2022

Feature	Description	Link
Class fields & private methods	Public/static/#private fields and methods	MDN
Top-level await	Use await at module top level	MDN
.at() method	Relative indexing with negative indices	MDN
Object.hasOwn	Safer replacement for hasOwnProperty	MDN
Error cause	new Error("msg", { cause }) for chained errors	MDN
RegExp Match Indices (d flag)	exec() results include .indices	MDN
Class static {} blocks	Static initialization logic in class body	MDN

const last = arr.at(-1);

class Counter {
  #count = 0;
  increment() { this.#count++; }
}

ES2021

Feature	Description	Link
String.prototype.replaceAll	Replace all occurrences without regex	MDN
Promise.any	Resolves with first fulfilled; rejects with AggregateError	MDN
Logical assignment (&&=, ||=, ??=)	Combine logical operators with assignment	MDN
Numeric separators	1_000_000 for readable numbers	MDN
WeakRef & FinalizationRegistry	Weak references and GC callbacks	MDN

const text = "aabbcc".replaceAll("b", "x"); // "aaxxcc"

user.name ??= "Anonymous";

ES2020

Feature	Description	Link
Optional chaining (?.)	Safe property access through nullable chains	MDN
Nullish coalescing (??)	Default only for null/undefined, not falsy	MDN
BigInt	Arbitrary-precision integers (123n)	MDN
Promise.allSettled	Waits for all promises regardless of outcome	MDN
globalThis	Universal global object across environments	MDN
Dynamic import()	On-demand module loading	MDN
String.prototype.matchAll	Iterator of all regex matches with groups	MDN
import.meta	Host-specific module metadata	MDN

const name = user?.profile?.name ?? "Anonymous";

const module = await import("./feature.js");

ES2019

Feature	Description	Link
Array.prototype.flat / flatMap	Flatten nested arrays; map then flatten	MDN
Object.fromEntries	Create object from key-value pairs	MDN
String.prototype.trimStart/trimEnd	Trim whitespace from one end	MDN
Optional catch binding	catch {} without parameter	MDN
Symbol.prototype.description	Direct access to Symbol's description	MDN
Stable Array.prototype.sort	Sort guaranteed to be stable	MDN

const flat = [[1, 2], [3, 4]].flat(); // [1, 2, 3, 4]

const obj = Object.fromEntries(new URLSearchParams("a=1&b=2"));

ES2018

Feature	Description	Link
Object rest/spread ({...obj})	Spread properties for objects	MDN
Async iteration (for await...of)	Iterate over async iterables	MDN
Promise.prototype.finally	Callback after promise settles	MDN
RegExp named capture groups	(?<name>...) syntax	MDN
RegExp s (dotAll) flag	. matches line terminators	MDN
RegExp lookbehind assertions	(?<=...) and (?<!...)	MDN
RegExp Unicode property escapes	\p{Script=Greek} with u flag	MDN

const { a, ...rest } = { a: 1, b: 2, c: 3 }; // rest = { b: 2, c: 3 }

for await (const chunk of readableStream) {
  process(chunk);
}

ES2017

Feature	Description	Link
async / await	Syntactic sugar for promise-based async code	MDN
Object.values / Object.entries	Get own enumerable values or [key, value] pairs	MDN
String.prototype.padStart/padEnd	Pad string to target length	MDN
Object.getOwnPropertyDescriptors	All own property descriptors for proper cloning	MDN
SharedArrayBuffer & Atomics	Shared memory for multi-threaded JS	MDN
Trailing commas in function params	Allowed in parameter lists and arguments	MDN

async function fetchData() {
  const response = await fetch(url);
  return response.json();
}

ES2016

Feature	Description	Link
Array.prototype.includes	Check if array contains element (handles NaN)	MDN
Exponentiation operator (**)	2 ** 4 instead of Math.pow(2, 4)	MDN

[1, 2, NaN].includes(NaN); // true
2 ** 10; // 1024

ES2015 (ES6)

Syntax

Feature	Description	Link
let and const	Block-scoped variable declarations	MDN
Arrow functions	() => {} with lexical this	MDN
Template literals	`Hello ${name}` — interpolation and multiline	MDN
Destructuring	Extract values from arrays/objects	MDN
Default parameters	function f(x = 1)	MDN
Rest/spread (...)	Rest params and array spread	MDN
Classes	class / extends / super	MDN
Generators (function*)	Pausable functions yielding values	MDN

Built-ins

Feature	Description	Link
Promises	Built-in async primitives	MDN
Symbol	New primitive for unique identifiers	MDN
Map / Set	New collection types	MDN
WeakMap / WeakSet	GC-friendly collections	MDN
Proxy / Reflect	Meta-programming via traps	MDN
Iterators & for...of	Iteration protocol and loop	MDN
Typed Arrays	ArrayBuffer, DataView, typed views	MDN
Object.assign	Shallow-copy/merge objects	MDN
Array.from / Array.of	Create arrays from iterables or arguments	MDN
String methods	includes, startsWith, endsWith, repeat	MDN
Number methods	isFinite, isNaN, isInteger, isSafeInteger	MDN

Modules

Feature	Description	Link
import / export	Native ES module system	MDN

const [first, ...rest] = [1, 2, 3, 4];

const greet = (name = "world") => `Hello, ${name}!`;

class Animal {
  constructor(name) { this.name = name; }
  speak() { return `${this.name} makes a noise.`; }
}

Further Reading

• Exploring JS — In-depth free books on every ES version by Dr. Axel Rauschmayer
• TC39 Proposals — Track upcoming JavaScript features
• What's new in ECMAScript — Paweł Grzybek's annual feature roundup
• JavaScript & TypeScript — Learning resources for JS and TS