2. History and Versions

The Origins

ECMAScript was born out of the need to standardize JavaScript implementations across different browsers. In the mid-1990s, Netscape created JavaScript, while Microsoft developed JScript. This led to compatibility issues.

ECMAScript 1 (1997)

• First standardized version
• Based on JavaScript 1.1
• Basic language features: variables, functions, objects, arrays

ECMAScript 2 (1998)

• Minor updates and clarifications
• Alignment with ISO/IEC 16262 standard

ECMAScript 3 (1999)

• Major update with significant new features:
  • Regular expressions
  • Better string handling
  • try/catch exception handling
  • do-while loops
  • in and instanceof operators

ECMAScript 4 (Abandoned)

• Ambitious update planned for 2000
• Too many changes caused controversy
• Eventually abandoned in 2008

ECMAScript 5 (2009)

• Focus on bug fixes and minor improvements
• Added "strict mode"
• JSON support
• New array methods: forEach, map, filter, reduce
• Object.create(), Object.defineProperty()

ECMAScript 6 / ES2015 (2015)

• Major overhaul with many new features:
  • let and const declarations
  • Arrow functions
  • Classes
  • Modules
  • Promises
  • Template literals
  • Destructuring
  • Default parameters
  • Rest/spread operators

ECMAScript 2016 (ES7)

• Array.prototype.includes()
• Exponentiation operator (**)

ECMAScript 2017 (ES8)

• async/await
• Object.values(), Object.entries()
• String padding methods
• Trailing commas in function parameters

ECMAScript 2018 (ES9)

• Asynchronous iteration
• Rest/spread properties
• Promise.finally()
• Regular expression improvements

ECMAScript 2019 (ES10)

• Array.prototype.flat()
• Object.fromEntries()
• String.prototype.trimStart() and trimEnd()
• Optional catch binding

ECMAScript 2020 (ES11)

• BigInt
• Dynamic imports
• Promise.allSettled()
• Nullish coalescing operator (??)
• Optional chaining (?.)

ECMAScript 2021 (ES12)

• String.prototype.replaceAll()
• Numeric separators
• Logical assignment operators (&&=, ||=, ??=)
• Promise.any()

ECMAScript 2022 (ES13)

• Top-level await
• Class field declarations
• Private methods and fields
• Ergonomic brand checks

ECMAScript 2023 (ES14)

• Array.prototype.findLast() and findLastIndex()
• Hashbang grammar
• Symbols as WeakMap keys

ECMAScript 2024 (ES15)

• Array grouping: Array.prototype.group and groupToMap()
• Promise.withResolvers() for ergonomic deferred Promises
• RegExp v flag with Unicode set notation and properties of strings
• Resizable/growable ArrayBuffer and SharedArrayBuffer
• ArrayBuffer.prototype.transfer() and transferToFixedLength()
• Atomics.waitAsync
• Well-formed Unicode strings

ECMAScript 2025 (ES16)

• New Set methods: union, intersection, difference, symmetricDifference, isSubsetOf, isSupersetOf, isDisjointFrom
• Iterator helpers (sync): Iterator.from, .map, .filter, .take, .drop, .flatMap, .reduce, .toArray, .forEach, .some, .every, .find
• Promise.try() to wrap sync/async functions with same-tick semantics
• JSON Modules and Import Attributes: import data from "./data.json" with { type: "json" }
• RegExp modifiers: scoped flag changes like (?i:...)
• Duplicate named capture groups in RegExp alternatives
• RegExp.escape() to safely escape strings for use in patterns
• Float16 support: Float16Array, DataView#getFloat16/setFloat16, Math.f16round

Current Status

As of 2025, ECMAScript continues to evolve with annual releases. ES2025 (ES16) is the latest edition, with broad support arriving in modern browsers and current Node.js versions.

Browser Support

• Modern browsers support ES6+ features
• Use tools like Babel for older browser compatibility
• Node.js supports most modern features

Version Naming Convention

• ES6 = ES2015
• ES7 = ES2016
• And so on...

Next Steps

Now that you understand ECMAScript's evolution, let's set up your development environment to start coding!