How do I find which version of V8 ships with a particular version of Node.js? If you keep this enabled, you should be prepared for further Node.js upgrades to break your code if V8 changes their semantics to more closely follow the standard. If you want to play safe, especially on production environments, consider removing this runtime flag until it ships by default on V8 and, consequently, on Node.js. As mentioned above, these are completed features that have not been considered stable yet. After all, it is now a synonym of -es_staging. The current behavior of the -harmony flag on Node.js is to enable staged features only. I have my infrastructure set up to leverage the -harmony flag. Please note that these are incomplete and possibly broken features of V8, so use them at your own risk: node -v8-options | grep 'in progress' You may list all the in progress features available on each Node.js release by grepping through the -v8-options argument. Generally speaking, expect them to land on a future Node.js release, although timing is unknown. New features are constantly being added to the V8 engine.

The website een provides an excellent overview over supported ECMAScript features in various versions of Node.js, based on kangax's compat-table. Which features ship with which Node.js version by default?

Note: these flags are exposed by V8 and will potentially change without any deprecation notice.

In progress features can be activated individually by their respective harmony flag, although this is highly discouraged unless for testing purposes.Staged features, which are almost-completed features that are not considered stable by the V8 team, require a runtime flag: -harmony.All shipping features, which V8 considers stable, are turned on by default on Node.js and do NOT require any kind of runtime flag.By keeping up-to-date with the latest releases of this engine, we ensure new features from the JavaScript ECMA-262 specification are brought to Node.js developers in a timely manner, as well as continued performance and stability improvements.Īll ECMAScript 2015 (ES6) features are split into three groups for shipping, staged, and in progress features: Node.js is built against modern versions of V8.

Es6 features