你可以使用控制台。firebug中的配置文件

大多数浏览器现在都在performance.now()中实现了高分辨率的计时。在性能测试方面，它优于new Date()，因为它独立于系统时钟运行。

使用

var start = performance.now();

// code being timed...

var duration = performance.now() - start;

参考文献

https://developer.mozilla.org/en-US/docs/Web/API/Performance.now () http://www.w3.org/TR/hr-time/#dom-performance-now

下面是一个简单的函数，显示传入函数的执行时间:

var perf = function(testName, fn) {
    var startTime = new Date().getTime();
    fn();
    var endTime = new Date().getTime();
    console.log(testName + ": " + (endTime - startTime) + "ms");
}

下面是一个用于时间性能的可重用类。示例包含在代码中:

/*
     Help track time lapse - tells you the time difference between each "check()" and since the "start()"

 */
var TimeCapture = function () {
    var start = new Date().getTime();
    var last = start;
    var now = start;
    this.start = function () {
        start = new Date().getTime();
    };
    this.check = function (message) {
        now = (new Date().getTime());
        console.log(message, 'START:', now - start, 'LAST:', now - last);
        last = now;
    };
};

//Example:
var time = new TimeCapture();
//begin tracking time
time.start();
//...do stuff
time.check('say something here')//look at your console for output
//..do more stuff
time.check('say something else')//look at your console for output
//..do more stuff
time.check('say something else one more time')//look at your console for output

迅速的回答

在jQuery上(更具体地说在Sizzle上)，我们使用这个(签出master并在浏览器上打开speed/index.html)，它反过来使用benchmark.js。这用于对库进行性能测试。

长回答

如果读者不知道基准测试、工作负载和分析器之间的区别，请先阅读spec.org的“readme 1st”部分中的一些性能测试基础知识。这是针对系统测试的，但是理解这个基础也会有助于JS的性能测试。以下是一些最突出的结果:

What is a benchmark? A benchmark is "a standard of measurement or evaluation" (Webster’s II Dictionary). A computer benchmark is typically a computer program that performs a strictly defined set of operations - a workload - and returns some form of result - a metric - describing how the tested computer performed. Computer benchmark metrics usually measure speed: how fast was the workload completed; or throughput: how many workload units per unit time were completed. Running the same computer benchmark on multiple computers allows a comparison to be made. Should I benchmark my own application? Ideally, the best comparison test for systems would be your own application with your own workload. Unfortunately, it is often impractical to get a wide base of reliable, repeatable and comparable measurements for different systems using your own application with your own workload. Problems might include generation of a good test case, confidentiality concerns, difficulty ensuring comparable conditions, time, money, or other constraints. If not my own application, then what? You may wish to consider using standardized benchmarks as a reference point. Ideally, a standardized benchmark will be portable, and may already have been run on the platforms that you are interested in. However, before you consider the results you need to be sure that you understand the correlation between your application/computing needs and what the benchmark is measuring. Are the benchmarks similar to the kinds of applications you run? Do the workloads have similar characteristics? Based on your answers to these questions, you can begin to see how the benchmark may approximate your reality. Note: A standardized benchmark can serve as reference point. Nevertheless, when you are doing vendor or product selection, SPEC does not claim that any standardized benchmark can replace benchmarking your own actual application.

性能测试JS

理想情况下，最好的性能测试是使用自己的应用程序和自己的工作负载来切换需要测试的内容:不同的库、机器等。

如果这是不可行的(通常是不可行的)。重要的第一步:定义您的工作量。它应该反映应用程序的工作负载。在这次演讲中，Vyacheslav Egorov谈到了你应该避免的糟糕工作量。

然后，你可以使用benchmark.js这样的工具来帮助你收集指标，通常是速度或吞吐量。在Sizzle上，我们感兴趣的是比较修复或更改如何影响库的系统性能。

如果某些东西执行得非常糟糕，那么下一步就是寻找瓶颈。

如何找到瓶颈?分析器

分析javascript执行情况的最佳方法是什么?

JSLitmus是一个轻量级的工具，用于创建特别的JavaScript基准测试

让我们看看函数表达式和函数构造函数之间的性能:

<script src="JSLitmus.js"></script>
<script>

JSLitmus.test("new Function ... ", function() { 
    return new Function("for(var i=0; i<100; i++) {}"); 
});

JSLitmus.test("function() ...", function() { 
       return (function() { for(var i=0; i<100; i++) {}  });
});

</script>

我上面所做的是创建一个函数表达式和函数构造函数，执行相同的操作。结果如下:

FireFox性能结果

IE性能结果