CSSOM을 사용하여 JavaScript에서 CSS를 효율적으로 구문 분석하려면 어떻게 해야 합니까?

var rulesForCssText = function (styleContent) {
    var doc = document.implementation.createHTMLDocument(""),
        styleElement = document.createElement("style");

    styleElement.textContent = styleContent;
    // the style will only be parsed once it is added to a document
    doc.body.appendChild(styleElement);

    return styleElement.sheet.cssRules;
};

a {
  color: red;
}

const rules = rulesForCssText('a { color: red; }');
const aRule = rules[0];
console.log(aRule.selectorText); // Outputs: "a"
console.log(aRule.style.color); // Outputs: "red"