ECMAScript 6 features available in Node.js 0.12

Question

A new stable release of Node.js (0.12) has landed recently with an upgraded Google's v8 JavaScript engine, v3.28.73.

What ECMAScript 6 features are currently present in Node.js, without using the --harmony flag?

I have checked several sites claiming to list the ES 6 features but all of them seem out of date - most prominently, this table (Update: now updated with current Node.js status as of 0.12), because several of the features are listed as requiring the --harmony flag while I found some of them being enabled by default (Maps, Sets, Symbols, to name a few). Update: Node specific tables have since been made available

Also, trying to google this information purely for the v8 engine gives too up-to-date information - current v8 release is 4.2.*, which is quite ahead of what Node.js uses.

My hopes are that this question (and its answers) will become a comprehensive summary on what ES 6 features are now available to Node.js developers.

ES 6 features enabled in Node.js 0.12 I currently know of:

• Maps, Sets / WeakMaps, WeakSets
• Symbols
• Object.observe
• Promises
• Number
  • .isInteger
  • .isSafeInteger
  • .isNaN
  • .EPSILON
  • .MIN_SAFE_INTEGER
  • .MAX_SAFE_INTEGER
• Math
  • .clz32
  • .imul
  • .sign
  • .log10
  • .log2
  • .log1p
  • .expm1
  • .cosh
  • .sinh
  • .tanh
  • .acosh
  • .asinh
  • .atanh
  • .trunc
  • .fround
  • .cbrt
  • .hypot

Answer 1

Features without --harmony flag:

• "for-of" loop
• Map, Set, WeakMap, WeakSet (already specified in question)
• Symbol (already specified in question)
• Promise (already specified in question)
• Array methods:
  • .keys()
  • .values()
  • .entries()
  • [Symbol.iterator]
• Object:
  • .observe() (initially was planned for ES7, but was removed from the spec entirely on November 2, 2015)
  • .is()
  • .setPrototypeOf()
  • .getOwnPropertySymbols()
  • .getNotifier() (not es6, example here)
  • .apply() and .call() (not es6, same purpose as Funciton.prototype.call and Function.prototype.apply)
• Number properties and methods (already specified in question)
  • .isInteger()
  • .isSafeInteger()
  • .isNaN()
  • .isFinite()
  • EPSILON
  • MIN_SAFE_INTEGER
  • MAX_SAFE_INTEGER
• Math methods (a lot of them) (already specified in question)
• constants

I thinks that's all that we have without --harmony flag.

Features with --harmony flag:

• generators
• arrow functions (without need of --harmony_arrow_functions flag in contrast to io.js)
• let variables - only in strict mode
• Binary and octal literals

• String methods:

  • .contains() (was replaced by includes() in actual ES6 specification)
  • .startsWith()
  • .endsWith()
  • .codePointAt()
  • .repeat()
  • .normalize()
  • String.fromCodePoint

• Proxy (behind the --harmony-proxies flag)

I think that's all. Maybe if I forgot something - I'll add it later to the list.