如何用回调来衡量javascript代码的执行时间

叁歲伎倆 2023-03-03 14:25 3阅读 0赞

本文翻译自：[How to measure execution time of javascript code with callbacks][]

*I have a piece of javascript code that I am executing using the node.js interpreter.* **我有一段javascript代码，我正在使用node.js解释器执行。**

for(var i = 1; i < LIMIT; i++){
        db.users.save({id : i, name : "MongoUser [" + i + "]"}, function(err, saved) {
              if( err || !saved ) console.log("Error");
              else console.log("Saved");
        });
    }

*I want to know how to measure the time taken by these db insert operations.* **我想知道如何测量这些数据库插入操作所花费的时间。** *I could compute the difference of Date values after and before this piece of code but that would be incorrect because of the asynchronous nature of the code.* **我可以计算这段代码之前和之前的Date值的差异，但由于代码的异步性质，这将是不正确的。**

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### \#1楼 ###

参考：[https://stackoom.com/question/IxZ4/如何用回调来衡量javascript代码的执行时间][https_stackoom.com_question_IxZ4_javascript]

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### \#2楼 ###

*You could give [Benchmark.js][] a try.* **您可以试试[Benchmark.js][] 。** *It supports many platforms among them also node.js.* **它支持其中的许多平台node.js.**

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### \#3楼 ###

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### \#4楼 ###

*There is a method that is designed for this.* **有一种专门为此而设计的方法。** *Check out [process.hrtime();][process.hrtime]* **查看[process.hrtime（）;][process.hrtime]** *.* **。**

*So, I basically put this at the top of my app.* **所以，我基本上把它放在我的应用程序的顶部。**

var start = process.hrtime();
    
    var elapsed_time = function(note){
        var precision = 3; // 3 decimal places
        var elapsed = process.hrtime(start)[1] / 1000000; // divide by a million to get nano to milli
        console.log(process.hrtime(start)[0] + " s, " + elapsed.toFixed(precision) + " ms - " + note); // print message + time
        start = process.hrtime(); // reset the timer
    }

*Then I use it to see how long functions take.* **然后我用它来看看函数需要多长时间。** *Here's a basic example that prints the contents of a text file called "output.txt":* **这是打印名为“output.txt”的文本文件内容的基本示例：**

*Here's a quick test you can run in a terminal (BASH shell):* **这是一个可以在终端（BASH shell）中运行的快速测试：**

for i in {1..100}; do echo $i; curl http://localhost:8080/; done

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### \#5楼 ###

*Use the Node.js [`console.time()`][console.time] and [`console.timeEnd()`][console.timeEnd] :* **使用Node.js [`console.time()`][console.time]和[`console.timeEnd()`][console.timeEnd] ：**

var i;
    console.time("dbsave");
    
    for(i = 1; i < LIMIT; i++){
        db.users.save({id : i, name : "MongoUser [" + i + "]"}, end);
    }
    
    end = function(err, saved) {
        console.log(( err || !saved )?"Error":"Saved");
        if(--i === 1){console.timeEnd("dbsave");}
    };

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### \#6楼 ###

*Invoking `console.time('label')` will record the current time in milliseconds, then later calling `console.timeEnd('label')` will display the duration from that point.* **调用`console.time('label')`将以毫秒为单位记录当前时间，然后调用`console.timeEnd('label')`将显示该点的持续时间。**

*The time in milliseconds will be automatically printed alongside the label, so you don't have to make a separate call to console.log to print a label:* **以毫秒为单位的时间将自动与标签一起打印，因此您无需单独调用console.log来打印标签：**

console.time('test');
    //some code
    console.timeEnd('test'); //Prints something like that-> test: 11374.004ms

*For more information, see [Mozilla's developer docs on `console.time`][Mozilla_s developer docs on _console.time] .* **有关更多信息，请参阅[有关`console.time` Mozilla开发人员文档][Mozilla_s developer docs on _console.time] 。**

[How to measure execution time of javascript code with callbacks]: https://oldbug.net/q/IxZ4/How-to-measure-execution-time-of-javascript-code-with-callbacks
[https_stackoom.com_question_IxZ4_javascript]: https://stackoom.com/question/IxZ4/%E5%A6%82%E4%BD%95%E7%94%A8%E5%9B%9E%E8%B0%83%E6%9D%A5%E8%A1%A1%E9%87%8Fjavascript%E4%BB%A3%E7%A0%81%E7%9A%84%E6%89%A7%E8%A1%8C%E6%97%B6%E9%97%B4
[Benchmark.js]: http://benchmarkjs.com/
[process.hrtime]: http://nodejs.org/docs/v0.8.0/api/all.html#all_process_hrtime
[console.time]: http://nodejs.org/api/console.html#console_console_time_label
[console.timeEnd]: http://nodejs.org/api/console.html#console_console_timeend_label
[Mozilla_s developer docs on _console.time]: https://developer.mozilla.org/en-US/docs/Web/API/Console/time