What version of Javascript is supported in node.js

I'm getting started with Node.js and I'm having a hard time figuring out what version of JavaScript is supported by node which makes it difficult figuring out what features I can use. Here's what I know.

• Node uses V8
• V8 implements ECMAScript as specified in ECMA-262, 3rd edition
• ECMA-262, 3rd edition is JavaScript 1.5

Given this, I would assume I can use JavaScript 1.5 compatible code in node. However, it turns out I can use the Array.forEach, among other constructs, even though according to MDC it isn't available until Javascript 1.6 -- ECMA-262, 5th edition.

Where am I going wrong? Is there a document somewhere that details the available language features?

Solution 1:

This matrix (V8 follows the WebKit column fairly closely) seems to pretty well answer the question "what features can I use?" but I can't find a canonical answer to "what version of javascript is supported?" As far as I can tell, the best answer is this: ECMA-262 3rd edition is supported, but many features of the 5th edition are also supported.

There's a good explanation of why V8 follows the WebKit and JavaScriptCore functionality on this thread.

Solution 2:

The Node javascript version depends on which version of v8 that Node uses. Node version 0.5.1 (14 Jul 2011) and upwards use v8 3.4.10 or later, and are 5th edition ECMA-262, rather than 3rd Edition. 5th edition is equivalent to Javascript 1.8.5. See below reasons.

Between 21 May 2011 and 15 June 2011 the v8 website stopped listing v8 as implementing 3rd edition ECMA-262 and started showing 5th edition. http://web.archive.org/web/20110521053630/http://code.google.com/p/v8/ http://web.archive.org/web/20110615102350/http://code.google.com/p/v8/

According to the v8 changelog, on the 15 June 2011 v8 changed to version 3.4.4. So that version and later are 5th edition.

According to the Node changelog, v8 3.4.10 was in Node Version 0.5.1, 14 Jul 2011, so that version and later are 5th edition ECMA-26. This does not mean that v8 versions before 3.4.10 were purely 3rd edition though, since there may have been a steady transition from 3rd to 5th through many v8 versions.