JScript vs. JavaScript differences
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From: VK on 25 Apr 2010 18:17 I propose to collect all known differences between JScript vs. JavaScript engines. I am using neutral word "difference" because the I don't want to transform it into yet another discussion about the eternal of "one who's name should not be spelled" etc. Simply: they do like that, X does like that, be warned. It also only and exclusively about pure Javascript engine, so even window.alert, confirm, prompt are out for now. Only the engine, Global and down. My initial contribution: Two "God's Bugs", because subjects of special hate and obsession of Brendan Eich himself: GB1) Named FunctionExpression treatment GB2) Terminal elision treatment. That one I remind is that var arr = [0,1,] window.alert(arr.length); // al. == 2 // IE == 3 1) Pending comma in object initializer. var foo = { 'a':1, 'b':2, } // al. OK // IE gives syntax error Maybe a distant relative of GB2 above. Can be very nasty without a possibility of parallel testing on IE as occasional typo will not be noticed, so be warned. Anyone else? ;-)
From: Stefan Weiss on 25 Apr 2010 18:37 On 26/04/10 00:17, VK wrote: > I propose to collect all known differences between JScript vs. > JavaScript engines. Between JScript and JavaScript or between JScript and ECMAScript? In this context, the word "JavaScript" really is ambiguous; it appears to refer exclusively to Netscape/Mozilla's implementation. You could start with this document: "[MS-ES3EX]: Microsoft JScript Extensions to the ECMAScript Language Specification Third Edition" http://msdn.microsoft.com/en-us/library/ff521046(VS.85).aspx It's quite current, has been discussed here, and is even linked from the FAQ. -- stefan
From: VK on 25 Apr 2010 18:55 On Apr 26, 2:37 am, Stefan Weiss <krewech...(a)gmail.com> wrote: > On 26/04/10 00:17, VK wrote: > > > I propose to collect all known differences between JScript vs. > > JavaScript engines. > > Between JScript and JavaScript or between JScript and ECMAScript? In > this context, the word "JavaScript" really is ambiguous; it appears to > refer exclusively to Netscape/Mozilla's implementation. For me there is only JavaScript. I don't know what "ECMAScript" and don't want to know. Yet to not transform it into a fruitless rwar discussion, let say JScript vs. all other prominent implementations. If "prominent implementations" absolutely necessarily requires a separate fruitless rwar discussion, let's say like this: "Microsoft JScript and Mozilla Firefox ECMA-262 3rd. ed. part implementations: differences between them" Any political correctness objections to that? > You could start with this document: "[MS-ES3EX]: Microsoft JScript > Extensions to the ECMAScript Language Specification Third Edition"http://msdn.microsoft.com/en-us/library/ff521046(VS.85).aspx Who the hey cares about *extensions"? And who out of average coders will study this documents in hope to see something useful for future use? Let's make a small thing that no one did yet: get together all implementation differences within the grammar defined in ECMA-262 3rd.ed. Then sort out i) important to know and ii) important for profound theoretical discussions only. Say GB2 is of the 2nd kind IMHO. When the last time anyone used elision and how many average coders even know about it? From the other side - again IMHO - pending comma difference is important to know. Who ever coded manually knows how often one types extra comma automatically when filling the initializer.
From: VK on 25 Apr 2010 19:57 On Apr 26, 3:19 am, Stefan Weiss <krewech...(a)gmail.com> wrote: > Why did you ask for comments if you don't want to hear the answers? Sorry if being too aggressive but I am really frustrated with the group situation where many people are ready to talk about everything except the applied programming. There is no JavaScript, there are no prominent browsers, there is not this, there is not that, any code may fail on this or that browser with 0.0000000000001% market share, DOM 0 is non-standard extension that can be missed (sic!), XHR is not standard so better not used it (sic!), let's better talk about some fresh W3C paper... Microsoft JScript - Mozilla JavaScript, only parts implemented by requirements of ECMA-262 3rd.ed. It is not all - but 70%-90% coverage at once is good enough for a starter. P.S. In the linked MS document I searched for "elision" - zero matches. So whatever it is, it is already lesser full than my initial post. Again: I want to get together cases that people should be really aware while making their code. Something one once encountered and couldn't get what's wrong right away. Of course c.l.j. gurus never were in such situations, whatever they do and see is crystal clear to them by definition. Well, I am not so perfect as they are and such situations did and do occur with me. Maybe - just maybe - I am not alone of the kind. In this case some more contributions to this thread may follow.
From: Stefan Weiss on 25 Apr 2010 20:39
On 26/04/10 01:57, VK wrote: > On Apr 26, 3:19 am, Stefan Weiss <krewech...(a)gmail.com> wrote: >> Why did you ask for comments if you don't want to hear the answers? > > Sorry if being too aggressive but I am really frustrated with the > group situation where many people are ready to talk about everything > except the applied programming. Yeah, I overreacted too, sorry. It appears that the one who was embarrassing himself was I, because I linked the wrong document... That's the one I meant: "[MS-ES3]: Internet Explorer ECMA-262 ECMAScript Language Specification Standards Support Document" http://msdn.microsoft.com/en-us/library/ff520996(v=VS.85).aspx This one covers the syntax differences, and it does have a warning about the handling of elisions in the Array initializer: | JScript 5.x sets the length property in step 3 to Result(2)+1. For | example, an ArrayLiteral of the form [,] will have a length of 2 | instead of 1 as specified above. Sorry about the confusion. -- stefan |