Get CSS Style Property with Javascript

propertyFromStyleSheet.js

//  This function will return css text of a supplied css selector (must match exactly) or
//  it will return the property defined in the second argument.  Properties are individual 
//  properties not combined properties.
//
//  propertyFromStylesheet('some selector', 'some property');
//
// modified from http://stackoverflow.com/a/16779622


function propertyFromStylesheet() {
    var value;

    // Checks for Selector argument.
    if (typeof(arguments[0]) === 'undefined') throw "Error: no selector defined";

    var selector = arguments[0];

    //Checks for attribute.  If undefined cssText is returned.
    var attribute = (typeof(arguments[1]) != 'undefined') ? arguments[1] : null;

    [].some.call(document.styleSheets, function (sheet) {
        return [].some.call(sheet.rules, function (rule) {
            if (selector === rule.selectorText) {
            	  if (attribute) {
	                return [].some.call(rule.style, function (style) {
	                    if (attribute && attribute === style) {
	                        value = rule.style.getPropertyValue(attribute);
	                        return true;
	                    } 
	                    return false;
	                });
            	  } else {
            	  	value = rule.cssText;
                	return true;
                }
            }
            return false;
        });
    });

    return value;
}