fmp

[jadenben01]

(function () {
    /**
     * get first-meaningful-paint
     */
    if (!window.performance || !window.performance.timing || !window.MutationObserver) {
        getfmpCallback(0);
    }
    window.count = 0;
    window.time = 0;
    var observeTime = 30000;
    var observedPoints = [];
    var innerHeight = window.innerHeight;
    var timing = window.performance.timing;
    var startTime = timing.navigationStart || timing.fetchStart;
    var observer = new window.MutationObserver(function(){
        window.count++;
        var t = Date.now() - startTime;
        console.log(window.count);
        var start = Date.now();
        var score = getDomMark(document, 1);
        console.log((Date.now() - start) + "ms");
        console.log(t + " - fmp");
        window.time = window.time + (Date.now() - start);
        console.log(window.time + " - total")
        observedPoints.push({
            score: score,
            t: t
        });
        
    });
    observer.observe(document, {
        childList: true,
        subtree: true
    });;
    function getDomMark(dom, level) {
        var length = dom.children ? dom.children.length : 0;
        var sum = 0;
        var tagName = dom.tagName;
        if (tagName !== 'SCRIPT' && tagName !== 'STYLE' && tagName !== 'META' && tagName !== 'HEAD') {
          if (dom.getBoundingClientRect && dom.getBoundingClientRect().top < innerHeight) {
            sum += level * length;
          }
          if (length > 0) {
            var children = dom.children;
            for (var i = 0; i < length; i++) {
              sum += getDomMark(children[i], level + 1);
            }
          }
        }
        return sum;
    }

    setTimeout(function () {
        observer.disconnect();
        var rates = [];
        for (var i = 1; i < observedPoints.length; i++) {
            if (observedPoints[i].t !== observedPoints[i - 1].t) {
                rates.push({
                    t: observedPoints[i].t,
                    rate: observedPoints[i].score - observedPoints[i - 1].score
                });
            }
        }
        rates.sort(function (a, b) {
            return b.rate - a.rate;
        });
        if (rates.length > 0) {
            getfmpCallback(rates[0].t);
        } else {
            getfmpCallback(0);
        }
    }, observeTime);
    
    function getfmpCallback(fmp){
        alert(fmp);
        window.FirstScreenTime = fmp;
    }
})();