getCSSPropertyValue.js

getCSSPropertyValue.js

/**
* @example
* getCSSPropertyValue('.someClass', 'color');
*/
function getCSSPropertyValue (selectorText, propertyName) {
     function _getPropertyFromStyleSheet (ss, selectorText, propertyName) {
         let value = null;
         [...ss.cssRules].some((rule) => {
             if (rule.type === CSSRule.STYLE_RULE && 
                 rule.selectorText === selectorText
             ) {
                 value = rule.style.getPropertyValue(propertyName);
                 return true;
             }
         });
         return value;
     }
     let value = null;
     [...document.styleSheets].some((ss) => {
         value = _getPropertyFromStyleSheet(ss, selectorText, propertyName);
         return value;
     });
     return value;
}