OK first I just want to correct my previous answer slightly - the Web APIs are provided by a JavaScript Runtime Environment, which works with the JavaScript engine, I should have made that clear. The JavaScript engine is a standalone entity that can be run in a browser or another environment i.e. in NodeJS. But again, the JavaScript Runtime Environment is implemented by the browser so the point still stands.
To answer your follow-up Jonathan, essentially yes, since there is nothing very 'central' about the web. However, it's not really 'each browser', since many browsers including Chrome, Edge and a lot of lesser known browsers use Chromium, with is all the core functionality of Google Chrome, but just missing some surface-level features which other browsers add on. So the main different implementations of JavaScript are the ones in Safari and Firefox.
As for your questions Eduardo, as far as I'm aware these days there aren't really any discrepancies in the results they produce, aside from newer features of JavaScript not being supported in older browsers. I'm not sure what you mean about 'oddly unexpected' results?
In terms of the most optimised one, if you mean fastest, I don't have the knowledge in that area to say, though I would guess V8 as it's very popular and focused on high performance. I'm also not sure what you mean by the 'real thing', since they are all the 'real thing' if they meet the requirements of the ECMAScript spec. The original implementation was Brendan Eich's original build of SpiderMonkey for the Netscape browser, but SpiderMonkey has changed a lot since then.
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OK first I just want to correct my previous answer slightly - the Web APIs are provided by a JavaScript Runtime Environment, which works with the JavaScript engine, I should have made that clear. The JavaScript engine is a standalone entity that can be run in a browser or another environment i.e. in NodeJS. But again, the JavaScript Runtime Environment is implemented by the browser so the point still stands.
To answer your follow-up Jonathan, essentially yes, since there is nothing very 'central' about the web. However, it's not really 'each browser', since many browsers including Chrome, Edge and a lot of lesser known browsers use Chromium, with is all the core functionality of Google Chrome, but just missing some surface-level features which other browsers add on. So the main different implementations of JavaScript are the ones in Safari and Firefox.
As for your questions Eduardo, as far as I'm aware these days there aren't really any discrepancies in the results they produce, aside from newer features of JavaScript not being supported in older browsers. I'm not sure what you mean about 'oddly unexpected' results?
In terms of the most optimised one, if you mean fastest, I don't have the knowledge in that area to say, though I would guess V8 as it's very popular and focused on high performance. I'm also not sure what you mean by the 'real thing', since they are all the 'real thing' if they meet the requirements of the ECMAScript spec. The original implementation was Brendan Eich's original build of SpiderMonkey for the Netscape browser, but SpiderMonkey has changed a lot since then.