Naive ResourceTiming crawl of all IFRAMEs

resourcetiming-crawl.js

//
// Naive ResourceTiming crawl of all IFRAMEs.
//
// Based on https://github.com/SOASTA/boomerang/blob/master/plugins/restiming.js
// which you should use to deal with all of the caveats (e.g. startTime adjusting)
//

function isFrameAccessible(frame) {
    var dummy;

    try {
        // try to trigger cross-origin warnings
        dummy = frame.location && frame.location.href;
        dummy = frame.document;

        if (("performance" in frame) && frame.performance) {
            return true;
        }
    }
    catch (e) {
        // NOP
    }

    return false;
}

function crawlFrame(frame) {
    var entries = [];

    try {
        if (!isFrameAccessible(frame)) {
            return [];
        }

        if (frame.frames) {
            for (var i = 0; i < frame.frames.length; i++) {
                entries = entries.concat(crawlFrame(frame.frames[i]));
            }
        }

        if (typeof frame.performance.getEntriesByType !== "function") {
            return [];
        }

        // NOTE: startTime will be off unless fixed, see
        // https://github.com/SOASTA/soasta-boomerang/blob/soasta/plugins/restiming.js
        // for how.
        return entries.concat(frame.performance.getEntriesByType("resource"));
    } catch (e) {
        // NOP
    }

    return entries;
}