Detecting DOM Support in a browser....

Is this possible -- can somebody give me a code snippit to detect if a browser supports DOM level 1

generally, document.getElementById and document.createElement are useful object tests for this.

However, Opera 6 returns a function for createElement, even though it can't add the created element to the page. So to cater for that, I'd do something like this:

var agt = navigator.userAgent.toLowerCase();
var op6 = (agt.indexOf("opera/6")!=-1||agt.indexOf("opera 6")!=-1)?true:false;

var DOM = (typeof document.getElementById!="undefined" && typeof document.createElement!="undefined" && !op6)?true:false;

try testing for document.implementation

Originally posted by liorean
try testing for document.implementation

Much better :thumbsup: But isn't that DOM2 ?

Nope! See <http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001/ecma-script-language-binding.html>

cool :)

var dom1 = document.implementation && document.implementation.hasFeature('XML', '1.0') && document.implementation.hasFeature('HTML', '1.0');

That should be pretty accurate, if vendors do what they are supposed to.

Might be a good idea to remove the DOM1 XML check, as IE is stupid... and apparently so is Opera. hmph

var dom1 = document.implementation && document.implementation.hasFeature('HTML', '1.0');

Hey - using strict warnings?

try this

var dom1=('implementation' in document)&& document.implementation.hasFeature('HTML', '1.0');

or, a bit longer but more backwards compatible:

var dom1=(typeof document.implementation!='undefined')&& document.implementation.hasFeature('HTML', '1.0');

Originally posted by liorean
var dom1=('implementation' in document)

Hey that's interesting. I didn't realise you could use in like that :)

Yeah, I know. I've only seen it used internally in Mozilla/Netscape code before I started using it. I have no idea how the support for it is, except that op7, moz and jscript5.6 (comes with ie6, and a few other microsoft products) support it.


DevEdge JavaScript 1.5 Core Reference (http://devedge.netscape.com/library/manuals/2000/javascript/1.5/reference/ops.html#1066286) says it was introduced in JavaScript 1.4.


MSDN Library Scripting JScript (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/script56/html/js56jsoprin.asp) says it was introduced in JScript 1.0 (ie3).

Excellent; thanks. I shall have to run some tests .. :)

Well, please notify me of any results you find - I'm interested in how much I can use this.

I did a couple of different tests - one using implementation, and one using the images collection, like a control.

The results are mostly what you'd expect, but a couple of surprises in there:


var DOM = ("implementation" in document);

* moz (tested ns6.01 and moz1.3b): true
* netscape 3-4: error
* opera 7: false ... the first time you view the page in each Opera session, but true on refresh or if you visit it again in the same session
* opera 4-6: false
* ie6: true
* ie4-5: error
* safari: true


var DIM = ("images" in document);

* moz (ditto): true
* netscape 3-4: error
* opera 5-7: false
* opera 4: true!
* ie6: true
* ie4-5: error
* safari: true



You can see the test page at http://www.brothercake.com/Ref/in.html

A couple of things that have come up on further testing:

- ("implementation" in document) returns true for the mac version of Opera 6; but presumably you can't actually use it.

- given the strange O7 results, I did another set of tests using (typeof document.implementation). The results are interesting:

* moz (ns6.01 and moz1.3b): [object DOMImplementation]
* netscape 3-4: undefined
* opera 7: [object HTMLDOMImplementation]
* opera 4-6: undefined .. except:
* opera 6/mac: [object DOMImplementation] (but presumably you can't actually use it)
* opera 3: null
* ie6: [object]
* ie5/mac: [object Implementation] (?)
* ie5/win: undefined
* ie4: undefined
* safari: [object DOMImplementation]


What this suggest to me is that, as an object test for DOM1 support, document.implementation has some caveats -

1 - it's undefined in win/ie5 - which may or may not be appropriate

2 - it returns an object collection in the mac version of Opera 6, but presumably you can't actually use it.

3 - it returns null (rather than "undefined") in Opera 3


Updated test results (http://www.brothercake.com/Ref/in.html)

Wow- what a mess.
If you test also using document.implementation.hasFeature('HTML','1.0'), or even just testing for ('hasFeature' in document.implementation), what does that say?

I'm not at my computer right now, but I'll try those out later on.

Interesting ... ("hasFeature" in document.implementation); is similar to ("implementation" in document); - same anomoly in O7, but additionally creates errors in opera 4,5 and 6

Adding document.implementation.hasFeature('HTML','1.0')
to the typeof test produces consistent results, except for opera 3 which fails to return instead of returning null, and mac/opera 6 which returns false (thankfully!)

check it out (http://www.brothercake.com/Ref/in.html)

Have you reported the anomaly/bug to the opera crowd?

Originally posted by liorean
Have you reported the anomaly/bug to the opera crowd?

Yeah, soon as I found it.

Hmm, is there a difference if you apply it to user-created objects? I think I've seen such a difference in the for...in loop.

Oh, why didn't anybody add the useful:
object.each() {|i| do-somwthing-with-i-here} syntax from ruby to javascript?

Hmm, do you think you could add tests on user created objects to that test page, brothercake? How do they behave compared to host objects?

Yeah I reckon; it'll have to be tomorrow though ...

http://www.brothercake.com/Ref/in.html

I addd this test to it:

var myObj = new Object;
myObj.foo = "bar";
var FIM = ("foo" in myObj);

the results are what you'd expect, except for Opera - it returns true all the way to version 4!

It was as I suspected then - for..in worked on user created objects before host objects in ie - same is the case for [string] in [object] in opera.

I hope they fix this soon as op7 and ie5m are the only true gen5 browsers not supporting it.