Element Style Values with Plain JS

element_style_values.js

function getStyle(oElm, strCssRule){
    var strValue = '';
    if (document.defaultView && document.defaultView.getComputedStyle) strValue = document.defaultView.getComputedStyle(oElm, '').getPropertyValue(strCssRule);
    else if (oElm.currentStyle){
        strCssRule = strCssRule.replace(/\-(\w)/g, function (strMatch, p1){ return p1.toUpperCase(); });
        strValue = oElm.currentStyle[strCssRule];
    }
    return strValue;
}

//usage
getStyle(document.getElementById('slide-up'), 'padding-top');