readonly unsigned long length
The number of CSSRule objects in this CSSRuleList array.
item( )
Returns the CSSRule object at the specified position. Instead of explicitly calling this method, JavaScript allows you to simply treat the CSSRuleList object as an array and to index it using standard square-bracket array notation. If the specified index is too large, this method returns null.
This interface defines a read-only ordered list (i.e., an array) of CSSRule objects. The length property specifies the number of rules in the list, and the item( ) method allows you to retrieve the rule at a specified position. In JavaScript, CSSRuleList objects behave like JavaScript arrays, and you can query an element from the list using square-bracket array notation instead of calling the item( ) method. (Note, however, that you cannot assign new nodes into a CSSRuleList using square brackets.)
CSSMediaRule.cssRules, CSSStyleSheet.cssRules