How to get the applied style from an element, excluding the default user agent styles

There is a read only property of document called ‘styleSheets’.

var styleSheetList = document.styleSheets;

https://developer.mozilla.org/en-US/docs/Web/API/Document/styleSheets

By using this, you can reach all the styles which are applied by the author.

There is a similar question about this but not a duplicate, in here:

Is it possible to check if certain CSS properties are defined inside the style tag with Javascript?

You can get the applied style from an element, excluding the default user agent styles using the accepted answer of that question i just mentioned.

That answer didn’t supply the element’s own style attribute content, so i have improved the code a bit:

var proto = Element.prototype;
var slice = Function.call.bind(Array.prototype.slice);
var matches = Function.call.bind(proto.matchesSelector || 
                proto.mozMatchesSelector || proto.webkitMatchesSelector ||
                proto.msMatchesSelector || proto.oMatchesSelector);

// Returns true if a DOM Element matches a cssRule
var elementMatchCSSRule = function(element, cssRule) {
  return matches(element, cssRule.selectorText);
};

// Returns true if a property is defined in a cssRule
var propertyInCSSRule = function(prop, cssRule) {
  return prop in cssRule.style && cssRule.style[prop] !== "";
};

// Here we get the cssRules across all the stylesheets in one array
var cssRules = slice(document.styleSheets).reduce(function(rules, styleSheet) {
  return rules.concat(slice(styleSheet.cssRules));
}, []);




var getAppliedCss = function(elm) {
	// get only the css rules that matches that element
	var elementRules = cssRules.filter(elementMatchCSSRule.bind(null, elm));
	var rules =[];
	if(elementRules.length) {
		for(i = 0; i < elementRules.length; i++) {
			var e = elementRules[i];
			rules.push({
				order:i,
				text:e.cssText
			})
		}		
	}
	
	if(elm.getAttribute('style')) {
		rules.push({
				order:elementRules.length,
				text:elm.getAttribute('style')
			})
	}
	return rules;
}







function showStyle(){
var styleSheetList = document.styleSheets;
// get a reference to an element, then...
var div1 = document.getElementById("div1");

var rules = getAppliedCss(div1);

var str="";
for(i = 0; i < rules.length; i++) {
			var r = rules[i];
			str += '<br/>Style Order: ' + r.order + ' | Style Text: ' + r.text; 
		}		
		
	document.getElementById("p1").innerHTML = str;	

}

#div1 {
float:left;
width:100px;
}

div {
text-align:center;
}

<div id="div1" style="font-size:14px;">
	Lorem ipsum 
	</div>
<br/>
<br/>
<a href="https://stackoverflow.com/questions/42025329/javascript:;" onclick="showStyle()"> Show me the style. </a>
	<p id="p1"><p>

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