JSFiddle - React, Tailwind, and code Playground

HTML

<button id="save">get content</button>
<div id="holder">
    <div style="left:10px;top:20px;background-color:#000000;">hello</div>
    <div style="left:10px;top:20px;">World</div>
    <div style="left:10px;top:20px;background-color:#ff0000;">!</div>
</div>

CSS

#holder div
{
    position: abolute;
    width: 100px;
    height:100px;
    cursor: pointer;
    background-color:#00ff00;
}

JavaScript

$('button#save').click(onButtonClick);

function onButtonClick()
{
    // try 1
    css($('#holder'));
    alert($('#holder').html());
    
    // try 2
    $('#holder div').each(function(){
        css($(this));        
    });
    alert($('#holder').html());
    
    // last try?
    $('#holder').children('div').each(function(){
        css($(this));        
    });
    alert($('#holder').html());
}

function css(a){
    var sheets = document.styleSheets, o = {};
    for(var i in sheets) {
        var rules = sheets[i].rules || sheets[i].cssRules;
        for(var r in rules) {
            if(a.is(rules[r].selectorText)) {
                o = $.extend(o, css2json(rules[r].style), css2json(a.attr('style')));
            }
        }
    }
    return o;
}

function css2json(css){
        var s = {};
        if(!css) return s;
        if(css instanceof CSSStyleDeclaration) {
            for(var i in css) {
                if((css[i]).toLowerCase) {
                    s[(css[i]).toLowerCase()] = (css[css[i]]);
                }
            }
        } else if(typeof css == "string") {
            css = css.split("; ");          
            for (var i in css) {
                var l = css[i].split(": ");
                s[l[0].toLowerCase()] = (l[1]);
            };
        }
        return s;
    }