jQuery – How to get all styles/css (defined within internal/external document) with HTML of an element

outerHTML (not sure, you need it — just in case)

Limitations: CSSOM is used and stylesheets should be from the same origin.

function getElementChildrenAndStyles(selector) {
  var html = $(selector).outerHTML();

  selector = selector.split(",").map(function(subselector){
    return subselector + "," + subselector + " *";
  }).join(",");
  elts = $(selector);

  var rulesUsed = [];
  // main part: walking through all declared style rules
  // and checking, whether it is applied to some element
  sheets = document.styleSheets;
  for(var c = 0; c < sheets.length; c++) {
    var rules = sheets[c].rules || sheets[c].cssRules;
    for(var r = 0; r < rules.length; r++) {
      var selectorText = rules[r].selectorText;
      var matchedElts = $(selectorText);
      for (var i = 0; i < elts.length; i++) {
        if (matchedElts.index(elts[i]) != -1) {
          rulesUsed.push(rules[r]); break;
        }
      }
    }
  }
  var style = rulesUsed.map(function(cssRule){
    if (cssRule.style) {
      var cssText = cssRule.style.cssText.toLowerCase();
    } else {
      var cssText = cssRule.cssText;
    }
    // some beautifying of css
    return cssText.replace(/(\{|;)\s+/g, "\$1\n  ").replace(/\A\s+}/, "}");
    //                 set indent for css here ^ 
  }).join("\n");
  return "<style>\n" + style + "\n</style>\n\n" + html;
}

usage:

getElementChildrenAndStyles("#divId");