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Question

Javascript - what kind of declaration is this?

Answer 1

+4 A:

That's invalid syntax in JavaScript, so as written that cannot work.

UPDATE

The syntax is valid in ActionScript, and the part immediately after the colon (Vector2 here) indicates the type of the variable being declared; it's also apparently valid and means the same thing in the JavaScript-like scripting language in Unity, which it seems from Chuck's answer is apparently what the code was originally written for. From what I've just read about Unity's "JavaScript", it's not compatible with any version of the language and should not be called JavaScript.

Tim Down 2010-10-27 11:46:01

Downvoter: please explain. The question has now been retagged as ActionScript but at the time I answered, this was correct.

Tim Down 2010-10-27 12:00:06

they call it Javascript...

Digital Robot 2010-10-27 13:56:41

@Digital Robot: Yes, and that's what I'm objecting to. I'd prefer it if they stuck to calling it UnityScript. It's quite like JavaScript but also does its own thing (e.g. no anonymous functions) which means that it doesn't conform to any definition of JavaScript.

Tim Down 2010-10-27 14:19:01

Yes, I discovered that when I tried to googled for that kind of declaration using the keyword javascript and found nothing! :D

Digital Robot 2010-10-28 14:59:52

Answer 2

+10 A:

That is not JavaScript, it's ActionScript 3 or UnityScript. the : indicates a type declaration.

apphacker 2010-10-27 11:48:26

Exactly what i thought....

st0le 2010-10-27 11:49:37

I think a similar deceleration scheme was also considered for the ECMAScript 4 standard but that effort was abandoned.

Alexandre Jasmin 2010-10-27 11:52:22

ActionScript 3 is the basis for ecma 4

apphacker 2010-10-27 11:53:53

It's actually ECMAScript 4 upon which ActionScript 3 (and 2) are based. It is also, therefore, part of JavaScript 2 so the statement isn't exactly correct.

Lazarus 2010-10-27 11:56:34

Lazarus is wrong. ECMAScript4 has been abandoned. No browser or current JavaScript compiler will recognize that as valid syntax, neither Gecko, V8, Webkit, nor Rhino or Triton.

apphacker 2010-10-27 11:58:14

Except that no browser i know of actually uses Javascript 2, leaving only possibly node.js and other arcane environments that don't really matter yet.

cHao 2010-10-27 11:58:33

@cHao - Again... who said anything about browsers? Jeez.

Lazarus 2010-10-27 12:01:05

That is not valid syntax in node.js which uses v8. It will produce "SyntaxError: Unexpected token :" in node.js

apphacker 2010-10-27 12:01:49

@apphacker - Ever thought of looking further than the browser? Unity uses it and the example the OP has given is from Unity. And whether implemented, in development or abandoned, it **is** still valid JavaScript 2.0!

Lazarus 2010-10-27 12:05:56

@Lazarus: Until it's blessed by ECMA, there is no "valid JavaScript 2.0!". There's stuff that implements what would have been in JS2, but "valid" implies conformance to some standard, which does not exist.

cHao 2010-10-27 12:10:30

@Lazarus Yes it's UnityScript I came to the same conclusion but you beat me to it. I will add an unity tag to the question.

Alexandre Jasmin 2010-10-27 12:21:34

@cHao - Since when has ECMA been responsible for JavaScript?

Lazarus 2010-10-27 12:21:47

@apphacker - ECMAScript 4 has been scaled back and renamed Harmony but hardly abandoned. Harmony still includes classes.

Lazarus 2010-10-27 12:23:14

@Lazarus: Since Javascript has become all but a direct translation of the ECMAScript docs. ECMAScript even started out as JS, but got its name changed when it was standardized.

cHao 2010-10-27 12:24:35

@cHao - And still ECMA do not validate or approve JavaScript, it doesn't matter how you dress it up.

Lazarus 2010-10-27 12:28:06

@cHao - I expect you will back me up that there's no such thing as valid HTML5 based on your arguments.

Lazarus 2010-10-27 12:29:39

@Lazarus: Psh. Show me Javascript (real JS, not that "new, improved" non-standard flavor you keep going on about) that's not also valid ECMAScript...or ECMAScript that's not also valid JS. The two differ in very little but the name.

cHao 2010-10-27 12:34:26

@Lazarus: There isn't, til it's published somewhere (not in a draft, but in a real finished document) exactly what is and isn't HTML 5. That doesn't stop it from being useful, though, as most browsers implement it. *Unlike* this "valid JavaScript 2.0!" crap, which no browser and no common interpreter implements.

cHao 2010-10-27 12:36:51

@cHao - Ah... it has to be common implementation for it to be valid against a draft standard. Blimey, you are strict.

Lazarus 2010-10-27 12:38:58

@Lazarus: Yeah, cause i was around for the later part of the browser wars. Incompatibilities all over the place. It still isn't totally over (witness IE), but it's a hell of a lot better than it used to be. What i'm against is a return to that state of things, where everyone had their own little custom twist on everything. Standards are useful, even de facto standards, as they emphasize compatibility.

cHao 2010-10-27 12:43:56

In fact *Actionscript*, *JScript.NET* and *UnitityScript* all share this optional type deceleration scheme that was considered for ES4. I'm not going to debate if these language can be rightfully called Javascript or ECMAScript. This debate doesn't bring anything useful.

Alexandre Jasmin 2010-10-27 12:48:23

Well I actually prefer static typing so if new versions of JavaScript end up supporting : I would be happy. In any case, the question has been answered several times over.

apphacker 2010-10-27 12:51:03

@apphacker I'm sorry if I'm being pedantic but could you edit your post to remove the assertion that *"it's ActionScript 3"* since the OP code clearly is UnityScript.

Alexandre Jasmin 2010-10-27 13:18:37

@Alexandre, done.

apphacker 2010-10-27 17:03:26

Answer 3

+2 A:

Vector2 is a type declaration : http://www.cs.sjsu.edu/~rucker/asteroids/html/Vector2.html

Are you writing something for iOS? http://forum.unity3d.com/threads/51609-How-to-make-character-JUMP

Chuck 2010-10-27 12:04:07

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