Don't down vote this fellow's question, its perfectly valid and interesting.
First, you have to make a distinction between Javascript(ECMAScript) the language, and the API's that an environment makes available to it.
A good example of this is document.getElementById(). This is universally found in browsers, but you won't find this in Node.js (a server-side javascript environment using V8). Conversely, Node makes available Buffers which you won't find in any browser.
I think the best way to answer your question is to identify in the respective environments which version of ECMAScript they claim to support. Various versions of each browser support different versions of ECMAScript, or such as Internet Explorer where earlier versions supported a variant called JScript that didn't always tie directly to the published standards.
First, you have to make a distinction between Javascript(ECMAScript) the language, and the API's that an environment makes available to it.
A good example of this is document.getElementById(). This is universally found in browsers, but you won't find this in Node.js (a server-side javascript environment using V8). Conversely, Node makes available Buffers which you won't find in any browser.
I think the best way to answer your question is to identify in the respective environments which version of ECMAScript they claim to support. Various versions of each browser support different versions of ECMAScript, or such as Internet Explorer where earlier versions supported a variant called JScript that didn't always tie directly to the published standards.
The wikipedia page is a good place to start, http://en.wikipedia.org/wiki/ECMAScript.