Doc Class

class Doc {
  constructor(docId = null) {
    this.html = this.getDocAsHtml(docId);
    this.xml = XmlService.parse(this.html);
    this.root = this.xml.getRootElement();
  }

  getDocStyles() {
    let styleTag = this.root.getChildren()[0].getChildText("style");
    let regexStyles = styleTag.match(/(\.c\d+\{.*?\})/g);
    let styles = {}

    for (let i in regexStyles) {
      console.log(regexStyles[i])
      let className = regexStyles[i].match(/\.(c\d+)\{/)[1];

      let cssStyle = this.parseCSSText(regexStyles[i]).style;
      console.log(className, cssStyle)
      styles[className] = cssStyle
    }


    return styles
  }

  parseCSSText(cssText) {
    var cssTxt = cssText.replace(/\/\*(.|\s)*?\*\//g, " ").replace(/\s+/g, " ");
    var style = {}, [,ruleName,rule] = cssTxt.match(/ ?(.*?) ?{([^}]*)}/)||[,,cssTxt];
    var cssToJs = s => s.replace(/\W+\w/g, match => match.slice(-1).toUpperCase());
    var properties = rule.split(";").map(o => o.split(":").map(x => x && x.trim()));
    for (var [property, value] of properties) style[cssToJs(property)] = value;
    return {cssText, ruleName, style}
  }

  getDocAsHtml(docId) {
    let id = docId ? docId : DocumentApp.getActiveDocument().getId(); //get active doc if no ID is supplied
    let _ = DriveApp.getStorageUsed(); //needed to get Drive Scope requested
    let url = "https://docs.google.com/feeds/download/documents/export/Export?id=" + id + "&exportFormat=html";
    let param = {
      method: "get",
      headers: { "Authorization": "Bearer " + ScriptApp.getOAuthToken() },
      muteHttpExceptions: true,
    };
    let html = UrlFetchApp.fetch(url, param).getContentText();
    html = html.replace(`<meta content="text/html; charset=UTF-8" http-equiv="content-type">`, "");
    return HtmlService.createHtmlOutput(html).getContent();
  }
}