Page performance indicator
page receives the first byte duration (TTFB: time to first byte)
Above the fold loading time
DomReady time
Total page load time
monitoring method(t = performance.timing)
ttfb: t.responseStart - t.navigationStart
firstScreen: It is more troublesome to calculate the first screen time
(Suggested solution: If there is a picture, calculate the latest loading time of the picture in the first screen - navigatorStart, if there is no picture, t.domInteractive - t.navigatorStart)
domReady:
Only the time to process the dom: t.domComplete - t.responseEnd
Counting from the beginning: t.domComplete - t.navigatorStart
total: t.loadEventStart - t.navigationStart