I recently did a deep dive into the history of JavaScript standards:
(pre-ecmascript versions of JS not investigated)
EcmaScript 1(1997) = JavaScript 1.1 - missing many ES3 features (see below), of which exceptions are the unrecoverable thing.
EcmaScript 2(1998) - minimal changes, mostly deprecations and clarifications of intent, reserve Java keywords
EcmaScript 3(1999) - exceptions, regexes, switch, do-while, instanceof, undefined, strict equality, encodeURI* instead of escape, JSON, several methods on Object/String/Array/Date
EcmaScript 4(2003) - does not exist due to committee implosion
EcmaScript 5(2009) - strict mode, getters/setters, remove reservations of many Java keywords, add reservation for let/yield, debugger, many static functions of Object, Array.isArray, many Array methods, String().trim method, Date.now, Date().toISOString, Date().toJSON
EcmaScript 5.1(2011) - I did not notice any changes compared to ES5, likely just wording changes. This is the first one that's available in HTML rather than just PDF.
EcmaScript 6(2015) - classes, let/const, symbols, modules (in theory; it's $CURRENTYEAR and there are still major problems with them in practice), and all sorts of things (not listed)
EcmaScript 11(2020) - bigint, globalThis
If it were up to me, I'd restrict the web to ES3 with ES5 library features, let/const from ES6, and bigint/globalThis from ES2020. That gives correctness and convenience without tempting people to actually try to write complex logic in it.
There are still pre-ES6 implementations in the wild (not for the general web obviously) ... from what I've seen they're mostly ES5, sometimes with a few easy ES6 features added.