prebid-localstorage.js

    // Store ad tags in localStorage to enable reporting bad ads
    // TODO: This doesn't work if multiple ads are shown in one placement with googletag.pubads().refresh()
    googletag.pubads().addEventListener('slotRenderEnded', function (event) {
        if (typeof(localStorage) !== 'object') console.log('fail');
        if (event.slot.getResponseInformation() === null) return;

        var slotAdUnitPath = event.slot.getAdUnitPath();
        gpt_placements[slotAdUnitPath] = {};
        gpt_placements[slotAdUnitPath]['dfp'] = event.slot.getResponseInformation();
        gpt_placements[slotAdUnitPath]['dfp']['contentUrl'] = event.slot.getContentUrl();
        gpt_placements[slotAdUnitPath]['dfp']['queryId'] = event.slot.getEscapedQemQueryId();

        var adId = event.slot.getTargeting('hb_adid')[0];
        if (adId) {
            gpt_placements[slotAdUnitPath]['pbjs'] = pbjs.getAllWinningBids().filter(function (bid) {
                return bid.adId === adId;
            });
        }

        if (gpt_placements[slotAdUnitPath]['dfp']) {
            try {
                localStorage.setItem("pbad_" + window.performance.timing.navigationStart, JSON.stringify(gpt_placements));
                // Only store 20 items
                if (Object.keys(gpt_placements).length === 1) { // Only needs to run once
                    var storageKeys = Object.keys(localStorage).sort().filter(function (key) {
                        return key.substring(0, 5) === "pbad_";
                    });
                    while (storageKeys.length > 20) {
                        localStorage.removeItem(storageKeys.shift());
                    }
                }
            } catch (e) {
                console.log("Unable to save in LocalStorage");
            }
        }

    });