The read-only CSSStyleSheet property cssRules returns a live CSSRuleList which provides a real-time, up-to-date list of every CSS rule which comprises the stylesheet. Each item in the list is a CSSRule defining a single rule.

A live-updating CSSRuleList containing each of the CSS rules making up the stylesheet. Each entry in the rule list is a CSSRule object describing one rule making up the stylesheet.

Individual rules within the stylesheet can then be accessed by index:

const ruleList = document.styleSheets[0].cssRules;

for (let i = 0; i < ruleList.length; i++) {
  processRule(ruleList[i]);
}

Rules can also be accessed using for...of:

const ruleList = document.styleSheets[0].cssRules;

for (const rule of ruleList) {
  processRule(rule);
}

However, because CSSRule is not a proper array, you can't use forEach().

• CSS Object Model
• Using dynamic styling information