Doing that may have unexpected consequences. Instead you should div.style.setProperty('left', '42px', 'important')
This will overrule all other styles defined in stylesheets
I guess you misunderstand me. div.classname is the JQuery selector.
Maybe I did …
I started to debug your code and now I see that it does not enter the second function.
In my case there are 1st stylesheets which have no the cssRules, but the 3rd one does. But the rules varibale is undefined. This is similar problem which I had in my code previously. I was stucked with SOP, there was exception Security error. In your case there is not security exception but it seems like the browser refuses to access the object this way. Why it is undefined? It should not be. I can view the object in debugger but I cannot access it. It would be simpler if you would download my addon version for Firefox and try it on the same blog as I am doing the test.
Well, I guess it should be cssRules instead of rules. It seems that rules is not supported by Firefox
But this is cross-browser problem. Is it possible to use this? ({cssRules, rules}) ? Because you don’t know which browser will be used.
I see you are using Chrome. Happy man.
As (almost) always, MDN knows the answer:
Using only cssRules should do.
Unfortunatly, with the cssRules I hit the error I have spoken about 
You should try in Firefox.
SecurityError
Maybe is it problem with permissions to access the css file?
"permissions": ["storage", "tabs", "activeTab", "notifications"],
Hey, someone answers my question and post solution!
var rules;
for (var i = 0; i< document.styleSheets.length ;i++) {
try {
rules = sheets[i].cssRules;
} catch(err) {
console.log("error");
alert("error");
}
Great. Now I know that I can make it working.
Here is my program what I done. There maybe bugs still. It shows the idea of the project I am working on.
mynamespace.removeClass = function(node, selectorText, classNames){
for (var k in classNames)
{
var hasClass = new RegExp( "/" + classNames[k] + "/");
if ( hasClass.test(selectorText) )
node.removeClass(classNames[k]);
}
}
mynamespace.filterStyles = function(node, searchStyles ) {
var classNames = node.prop("className").split(" ");
var sheets = document.styleSheets, o = {};
var rules;
for (var i in sheets) {
// Firefox - Security fix:
try { rules = sheets[i].cssRules; } catch(err) {}
if(rules)
for (var r = 0; r < rules.length; r++) {
if (node.is(rules[r].selectorText))
{
var selector;
selector = mynamespace.searchRule(rules[r].style, searchStyles);
if (!selector)
selector = mynamespace.searchRule(node.attr('style'), searchStyles);
if (selector)
mynamespace.removeClass(node, selector, classNames);
}
}
}
return false;
}
/* searchRule searches rules,
compares with ss searchStyles,
returns selectorText if condition is true,
returns false if condition is false.
*/
mynamespace.searchRule = function(css, ss ) {
if (typeof css == "undefined" )
return false;
var selector = css.parentRule.selectorText;
if (css instanceof CSSStyleDeclaration) {
for (var i = 0; i<css.length; i++)
{
/*
var ss = {
position: { val: "relative", op: "=" },
left: { val: null , op: "" },
right: { val: null , op: "" },
top: { val: null , op: "" },
bottom: { val: null , op: "" },
float: { val: "none" , op: "!" , andop: "-" }
} */
for (var a in ss)
{
if ( a == css[i] )
{
if ( ss[a].val === null && css[a] )
return selector;
else
if ( ss[a].op == "=" && ss[a].val === css[a] )
return selector;
else
if ( ss[a].op == "!" )
{
if ( ss[a].hasOwnProperty("andop") )
{
if ( ss[a].andop == "-" )
{
if ( css[a] != "" )
return selector;
}
}
else
{
if( ss[a].val != css[a] )
return selector;
}
return selector;
}
}
} // end inner for
} // end outer for
} // if css instance of
else if (typeof css == "string") {
css = css.split("; ");
// not implemented
}
return false;
}
/* Implementation */
var searchStyles = {
position: { val: "absolute", op: "=" },
left: { val: null , op: "" },
right: { val: null , op: "" },
top: { val: null , op: "" },
bottom: { val: null , op: "" },
float: { val: "none" , op: "!" , andop: "-" }
}
var selectors = "div.fauxcolumn-right-outer;div.fauxcolumn-center-outer"
selectors = selectors.split(";");
var searches = [];
var targets = [];
for ( var k in selectors )
{
if ( (k % 2) == 0 )
searches.push(selectors[k]);
else
targets.push(selectors[k]);
}
for ( var k in searches )
{
search = $(searches[k]);
mynamespace.filterStyles(search, searchStyles);
target = $(targets[k]);
mynamespace.filterStyles(search, searchStyles);
}
If you see any bugs please let me know.
Is there a way to find out the stylesheets / style rules which were inserted into document?
Edit:
Yes it is. First answer here.
Modified and simplified version posted by me.