AymaneD · June 25, 2020 09:02 · Mar 28, 2013 · Mar 28, 2013
diff --git a/gistfile1.js b/gistfile1.js
@@ -0,0 +1,36 @@
+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));
+}, []);
+
+// Example of usage:
+
+// get a reference to an element, then...
+var bar = document.getElementById("bar");
+
+// get only the css rules that matches that element
+var elementRules = cssRules.filter(elementMatchCSSRule.bind(null, bar));
+
+// check if the property "width" is in one of those rules
+hasWidth = propertyInCSSRule.bind(null, "width");
+
+// Do something if `width` is defined in the element's rules
+if (elementRules.some(hasWidth)) {
+  // ...
+}
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