api: YAML JSON TOON Database
version: 1.0.0
format: toon
dataset:
  id: 2829
  slug: javascript-es6-features
  title: JavaScript ES6+ Features Reference
  description: "Key JavaScript features from ES6 through ES2022: arrow functions, template literals, destructuring, spread, async/await, optional chaining, nullish coalescing, and top-level await."
  summary: "JavaScript features introduced from ES2015 onward, each with the version and an example: arrow functions, template literals, destructuring, spread, async/await, optional chaining, nullish coalescing and top-level await, plus classes, modules, promises, generators, maps and sets, BigInt, private fields and newer array methods."
  use_when[2]: You need the ECMAScript version that introduced a feature and its syntax.,You are deciding what a browser or Node version supports.
  caveats[2]: Browser and runtime support lags the specification; check compatibility tables or a transpiler configuration.,Newer proposals appear on the standards track before they are final; the list covers shipped features.
  related[4]: typescript-type-system,browser-web-apis-reference,javascript-frameworks-comparison,language-comparison-2026
  entry_count: 20
  fields[4]{section,field,type,example}:
    features,name,string,Arrow Functions
    features,version,string,ES6 (2015)
    features,description,string,Concise function syntax with lexical this bindi…
    features,example,string,"const add = (a, b) => a + b;"
  category: Programming Languages
  category_slug: programming-languages
  tags: "javascript,es6,web,reference"
  view_count: 40
  created_at: 1777673262
  updated_at: 1777673262
data:
  features[20]{name,version,description,example}:
    Arrow Functions,ES6 (2015),Concise function syntax with lexical this binding,"const add = (a, b) => a + b;"
    Template Literals,ES6 (2015),"String interpolation with backticks and ${}","`Hello, ${name}!`"
    Destructuring,ES6 (2015),Unpack values from arrays or objects into variables,"const {name, age} = person;"
    Spread Operator,ES6 (2015),Expand iterables into individual elements,"const merged = [...arr1, ...arr2];"
    Async/Await,ES8 (2017),Syntactic sugar over Promises for async code,const data = await fetch(url);
    Optional Chaining,ES2020,Safe nested property access without null check,user?.profile?.name
    Nullish Coalescing,ES2020,Fallback for null/undefined only (not falsy),const x = value ?? defaultValue;
    Top-level Await,ES2022,Use await outside async functions in modules,const config = await loadConfig();
    Classes,ES6 (2015),Syntax for constructor functions and prototype-based inheritance,"class Animal { constructor(name) { this.name = name; } speak() { return this.name; } }"
    Modules,ES6 (2015),Standard import and export of code between files,"import { add } from './math.js'; export const pi = 3.14;"
    Promises,ES6 (2015),Objects representing the eventual result of an asynchronous operation,fetch(url).then(res => res.json()).catch(console.error)
    Generators,ES6 (2015),"Functions that can pause and resume, producing a sequence of values","function* count() { yield 1; yield 2; }"
    Map and Set,ES6 (2015),Collections with arbitrary keys and unique values,"const m = new Map([['a', 1]]); const s = new Set([1, 2, 2]);"
    Array.prototype.flat and flatMap,ES2019,Flatten nested arrays and map then flatten,"[1, [2, [3]]].flat(2) // [1, 2, 3]"
    Object.fromEntries,ES2019,Builds an object from key-value pairs,"Object.fromEntries([['a', 1], ['b', 2]]) // { a: 1, b: 2 }"
    BigInt,ES2020,Arbitrary-precision integers,2n ** 64n
    Logical Assignment,ES2021,Combine logical operators with assignment,a ||= 1; b &&= 2; c ??= 3;
    Private Class Fields,ES2022,Fields that are only accessible inside the class,"class C { #secret = 1; get() { return this.#secret; } }"
    Array.prototype.at,ES2022,Index with negative positions counting from the end,"[10, 20, 30].at(-1) // 30"
    Array.prototype.toSorted,ES2023,Sort a copy of an array without mutating it,"const sorted = arr.toSorted((a, b) => a - b);"