phantomas/modules/domMutations/scope.js

Headless Chromium-based web performance metrics collector and monitoring tool

(function DOMmutationsScope(phantomas) {
  if ("MutationObserver" in window) {
    // wait for DOM ready
    document.addEventListener("readystatechange", function () {
      if (document.readyState !== "interactive") {
        return;
      }

      phantomas.log("DOM query: setting up MutationObserver...");

      var observer = new MutationObserver(function (allmutations) {
        allmutations.map(function (mutation) {
          // @see https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver#MutationRecord
          var targetPath = phantomas.getDOMPath(
            mutation.target,
            true /* dontGoUpTheDom */
          );

          switch (mutation.type) {
            case "attributes":
              phantomas.log(
                'DOM mutation: "%s" attr (was "%s") set on %s',
                mutation.attributeName,
                mutation.oldValue || "",
                targetPath
              );

              phantomas.incrMetric("DOMmutationsAttributes");
              phantomas.addOffender("DOMmutationsAttributes", {
                attribute: mutation.attributeName,
                node: targetPath,
              });
              break;

            case "childList":
              var wereAdded = mutation.addedNodes.length > 0,
                nodes = wereAdded ? mutation.addedNodes : mutation.removedNodes,
                nodePath;

              for (var n = 0, nodesLen = nodes.length; n < nodesLen; n++) {
                nodePath = phantomas.getDOMPath(
                  nodes[n],
                  true /* dontGoUpTheDom */
                );

                phantomas.log(
                  'DOM mutation: node "%s" %s "%s"',
                  nodePath,
                  wereAdded ? "added to" : "removed from",
                  targetPath
                );

                if (wereAdded) {
                  phantomas.incrMetric("DOMmutationsInserts");
                  phantomas.addOffender("DOMmutationsInserts", {
                    node: nodePath,
                    target: targetPath,
                  });
                } else {
                  phantomas.incrMetric("DOMmutationsRemoves");
                  phantomas.addOffender("DOMmutationsRemoves", {
                    node: nodePath,
                    target: targetPath,
                  });
                }
              }
              break;

            default:
              phantomas.log("DOM mutation: %s", mutation.type);
          }
        });
      });

      observer.observe(document.body, {
        childList: true,
        attributes: true,
        characterData: true,
        subtree: true,
        attributeOldValue: true,
      });
    });
  } else {
    phantomas.log("DOM query: MutationObserver not available!");
  }
})(window.__phantomas);