List all used CSS classes

listAllUsedClassNames.js

(function listAllUsedClassNames () {
  var classNames = {};
  Array.prototype.forEach.call(document.querySelectorAll("*"), function (element) {
    if (typeof element.className === "string") {
      element.className.split(" ").forEach(function (className) {
        if (className) {
          classNames[className] = true;
        }
      });
    };
  });
  //console.log(Object.keys(classNames).sort().join("\n"));
  return Object.keys(classNames);
}());