The CSS Rule object

Question

According this site externalcss3 The CSS Rule object of the styleSheet object lets you access the individual rules of a stylesheet.

So If I try to run this piece of code(*) on stackoverflow page, using the javascript console, I expect to see some CSS Rules written in this page http://cdn.sstatic.net/stackoverflow/all.css?v=04e0337352b3.

(*)

var mysheet=document.styleSheets[0]
var myrules=mysheet.cssRules? mysheet.cssRules: mysheet.rules
for (i=0; i<myrules.length; i++) {
     console.log(myrules[i].selectorText.toLowerCase());
}

Actually the result of console.log is something different from what I would expect:

object[type="application/x-shockwave-flash"], object[type="application/futuresplash"], object[data*=".swf"], object[src*=".swf"], embed[type="application/x-shockwave-flash"], embed[type="application/futuresplash"], embed[src*=".swf"]

What have I Missed? Sorry for my ignorance and your time.

I actually find that there are no rules in the only stylesheet (0). Still weird. — Marcin
– Marcin, Commented May 17, 2012 at 18:16
I bet the stylesheet you are seeing is being injected by a browser extension... something like adblock, maybe (except adblock puts the stylesheet at the end, so must be something else). — Dagg Nabbit
– Dagg Nabbit, Commented May 17, 2012 at 19:11

Community · Accepted Answer · 2017-05-23 12:25:05Z

5

It seems you can only access the rules in the CSS file if they are from the same domain.

Read this thread: Reading the rules of a cross domain CSS file in DOM

edited May 23, 2017 at 12:25

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answered May 17, 2012 at 18:50

Joseph Silber

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2 Comments

apsillers Over a year ago

Definitely correct, although I am curious why the OP could read any rules at all.

Joseph Silber Over a year ago

@apsillers - I have no idea. I correctly get a TypeError: Cannot read property 'length' of null.

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