增加首屏检测

 var cookies = require('./cookie');
 
+// 首屏时间尝试：
+// 1,获取首屏基线高度
+// 2,计算出基线dom元素之上的所有图片元素
+// 3,所有图片onload之后为首屏显示时间
+// 参考 https://www.zhihu.com/question/23212408/answer/56647975
+//
+function getOffsetTop(ele) {
+    var offsetTop = ele.offsetTop;
+    if (ele.offsetParent !== null) {
+        offsetTop += getOffsetTop(ele.offsetParent);
+    }
+    return offsetTop;
+}
+
+var firstScreenHeight = window.screen.height;
+var firstScreenImgs = [];
+var isFindLastImg = false;
+var allImgLoaded = false;
+var firstScreenLoadTime = 0;
+var t = setInterval(function() {
+    var i, img;
+    if (isFindLastImg) {
+        if (firstScreenImgs.length) {
+            for (i = 0; i < firstScreenImgs.length; i++) {
+                img = firstScreenImgs[i];
+                if (!img.complete) {
+                    allImgLoaded = false;
+                    break;
+                } else {
+                    allImgLoaded = true;
+                }
+            }
+        } else {
+            allImgLoaded = true;
+        }
+        if (allImgLoaded) {
+            firstScreenLoadTime = (new Date()).getTime() - _timeStart
+            clearInterval(t);
+        }
+    } else {
+        var imgs = document.body.querySelector('img');
+        for (i = 0; i < imgs.length; i++) {
+            img = imgs[i];
+            var imgOffsetTop = getOffsetTop(img);
+            if (imgOffsetTop > firstScreenHeight) {
+                isFindLastImg = true;
+                break;
+            } else if (imgOffsetTop <= firstScreenHeight && !img.hasPushed) {
+                img.hasPushed = 1;
+                firstScreenImgs.push(img);
+            }
+        }
+    }
+}, 0);
+
+
 var reporter = {
     config: {
         reportUrl: '//analytics.m.yohobuy.com/yas.gif',
@@ -64,7 +120,7 @@ var reporter = {
         var self = this;
         var errorList = JSON.parse(cookies(this.config.errorKey) || '[]');
         var errStr = this.stringify(errorList);
-        
+
         this.report(errStr, function() {
             self.clearError();
         })
@@ -84,22 +140,40 @@ var reporter = {
         document.addEventListener && document.addEventListener('DOMContentLoaded', function(event) {
             timeList.push({
                 tp: 'dcl', // DOMContentLoaded
-                t: (new Date()) - _timeStart
+                t: (new Date()).getTime() - _timeStart
             });
+
+            // 首屏加载速度
+            var imgs = document.body.querySelector('img');
+            if (!imgs.length) {
+                isFindLastImg = true;
+            }
         })
 
         window.addEventListener && window.addEventListener('load', function(event) {
             timeList.push({
                 tp: 'ld', // load
-                t: (new Date()) - _timeStart
+                t: (new Date()).getTime() - _timeStart
             });
 
+            // 首屏加载速度
+            allImgLoaded = true;
+            isFindLastImg = true;
+            if (t) {
+                clearInterval(t);
+            }
+            if (firstScreenLoadTime) {
+                timeList.push({
+                    tp: 'fs', // firstScreenLoadTime
+                    t: firstScreenLoadTime
+                });
+            }
+
             timeList.push({
                 tp: 'pf', // performance
                 dcl: (window.performance && window.performance.timing.domComplete || 0) - pStart,
                 ld: (window.performance && window.performance.timing.loadEventStart || 0) - pStart
             });
-            
 
             self.reportTime(timeList); // 先上报 DOMContentLoaded，load 的时间
         });