4. An overview of ES2018 and ES2019

4.1. ECMAScript 2018

Major new features:

• Asynchronous Iteration (Domenic Denicola, Kevin Smith)
• Rest/Spread Properties (Sebastian Markbåge)

New regular expression features:

• RegExp named capture groups (Gorkem Yakin, Daniel Ehrenberg)
• RegExp Unicode Property Escapes (Mathias Bynens)
• RegExp Lookbehind Assertions (Gorkem Yakin, Nozomu Katō, Daniel Ehrenberg)
• s (dotAll) flag for regular expressions (Mathias Bynens)

Other new features:

• Promise.prototype.finally() (Jordan Harband)
• Template Literal Revision (Tim Disney)

4.2. ECMAScript 2019

Major new features:

• Array.prototype.{flat,flatMap} (Michael Ficarra, Brian Terlson, Mathias Bynens)
• Object.fromEntries (Darien Maillet Valentine)

Minor new features:

• String.prototype.{trimStart,trimEnd} (Sebastian Markbåge)
• Symbol.prototype.description (Michael Ficarra)
• Optional catch binding (Michael Ficarra)
• Array.prototype.sort() is guaranteed to be stable (Mathias Bynens).

Changes that are mostly internal:

• Well-formed JSON.stringify (Richard Gibson)
• JSON superset (Richard Gibson)
• Function.prototype.toString revision (Michael Ficarra)