javascript window.performance javascript的解释
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Explanation of window.performance javascript
提问by karthick
I am working on detecting the connection speed, so i planned to go with window.performanceobject for duration calculation.
我正在检测连接速度，所以我计划使用window.performance对象进行持续时间计算。
I am little confused with window.performance.timing object is generated based on the whole page load, or based on the last request and response.
我有点困惑 window.performance.timing 对象是基于整个页面加载生成的，还是基于最后一个请求和响应。
For Example:
例如：
I am having 5 server call for web page load, performance.timingobject is generated based on all the 5 server calls or based on the 5th server call(last call).
我有 5 个服务器调用来加载网页，performance.timing对象是基于所有 5 个服务器调用或基于第 5 个服务器调用（最后一次调用）生成的。
sample connection speed calculation for reference
示例连接速度计算供参考
var bitsLoaded = 100000; //bits total size of all files (5 server call).
var duration = performance.timing.responseEnd - performance.timing.navigationStart;
var speedBps = Math.round(bitsLoaded / duration);
var speedKbps = (speedBps / 1024).toFixed(2);
var speedMbps = (speedKbps / 1024).toFixed(2);
Anything not clear ready to explain
任何不清楚的准备解释
Any idea about window.performance
关于 window.performance 的任何想法
回答by Calvin Zhang
Not sure if this chart gives you a better understanding of performance.timing.
不确定此图表是否能让您更好地了解 performance.timing。
For your question:
对于您的问题：
I am having 5 server call for web page load, performance.timing object is generated based on all the 5 server calls or based on the 5th server call(last call).
我有 5 个服务器调用来加载网页，performance.timing 对象是基于所有 5 个服务器调用或基于第 5 个服务器调用（最后一次调用）生成的。
The answer is: performance.timingis generated based on all requests and responses(but not including the ajax ones).
答案是：performance.timing基于所有请求和响应（但不包括 ajax 的）生成。
For the sample connection speed calculation script you gave, I guess the below one is better.
对于您提供的示例连接速度计算脚本，我想下面的更好。
var duration = performance.timing.responseEnd - performance.timing.responseStart;
The reason is: the duration from navigationStartto responseEndincludes DNS timing which does not transfer any data from server to client.
原因是：从navigationStartto的持续时间responseEnd包括 DNS 计时，它不会将任何数据从服务器传输到客户端。
Please refer to https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/NavigationTiming/Overview.htmlfor the definition of timings.
时序定义请参考https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/NavigationTiming/Overview.html。
回答by DarrenVortex
performance.timing is NOT based on the last request and response. It measures the delay between navigationStartstage and loadEventStartstage in a page life cycle. As explained here, it's main use is to determine the Page Load Speed.
In my opinion. performance.timing can't really be used for measuring connection speed since it's initiated Afterthe user has received the response and is a javascript object, which runs on the browser. I suggest you simply ping the user and use the round trip time.
performance.timing 不是基于最后的请求和响应。它测量页面生命周期中navigationStart阶段和loadEventStart阶段之间的延迟。正如这里所解释的，它的主要用途是确定页面加载速度。
在我看来。performance.timing 不能真正用于测量连接速度，因为它是在用户收到响应后启动的，并且是一个 javascript 对象，它在浏览器上运行。我建议您简单地 ping 用户并使用往返时间。
