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

这是为特定操作收集性能信息的好方法。

start = new Date().getTime(); 
for (var n = 0; n < maxCount; n++) {
/* perform the operation to be measured *//
}
elapsed = new Date().getTime() - start;
assert(true,"Measured time: " + elapsed);

你可以使用这个:http://getfirebug.com/js.html。它有一个JavaScript分析器。

这是一个非常老的问题，但我认为我们可以提供一个基于es6的简单解决方案来快速测试你的代码。

这是用于执行时间的基本工作台。我们使用performance.now()来提高精度:

/** * Figure out how long it takes for a method to execute. * * @param {Function} method to test * @param {number} iterations number of executions. * @param {Array} list of set of args to pass in. * @param {T} context the context to call the method in. * @return {number} the time it took, in milliseconds to execute. */ const bench = (method, list, iterations, context) => { let start = 0 const timer = action => { const time = performance.now() switch (action) { case 'start': start = time return 0 case 'stop': const elapsed = time - start start = 0 return elapsed default: return time - start } }; const result = [] timer('start') list = [...list] for (let i = 0; i < iterations; i++) { for (const args of list) { result.push(method.apply(context, args)) } } const elapsed = timer('stop') console.log(`Called method [${method.name}] Mean: ${elapsed / iterations} Exec. time: ${elapsed}`) return elapsed } const fnc = () => {} const isFunction = (f) => f && f instanceof Function const isFunctionFaster = (f) => f && 'function' === typeof f class A {} function basicFnc(){} async function asyncFnc(){} const arrowFnc = ()=> {} const arrowRFnc = ()=> 1 // Not functions const obj = {} const arr = [] const str = 'function' const bol = true const num = 1 const a = new A() const list = [ [isFunction], [basicFnc], [arrowFnc], [arrowRFnc], [asyncFnc], [Array], [Date], [Object], [Number], [String], [Symbol], [A], [obj], [arr], [str], [bol], [num], [a], [null], [undefined], ] const e1 = bench(isFunction, list, 10000) const e2 = bench(isFunctionFaster, list, 10000) const rate = e2/e1 const percent = Math.abs(1 - rate)*100 console.log(`[isFunctionFaster] is ${(percent).toFixed(2)}% ${rate < 1 ? 'faster' : 'slower'} than [isFunction]`)

性能测试最近成了一个流行词，但这并不是说性能测试在QA中不是一个重要的过程，甚至在产品发布之后也不是。当我开发应用程序时，我使用了许多不同的工具，其中一些是上面提到的chrome Profiler，我通常会查看一个SaaS或一些开源的东西，我可以开始工作，然后忘记它，直到我收到警告，说有些东西出了问题。

有很多很棒的工具可以帮助您关注性能，而不需要您跳过一些基本的提醒设置。这里有一些我认为值得你自己去看看。

Sematext.com Datadog.com Uptime.com Smartbear.com Solarwinds.com

为了画出更清晰的画面，这里有一个关于如何为react应用程序设置监控的小教程。

我发现执行时间是最好的衡量标准。