How do you performance test JavaScript code

Question

CPU Cycles  Memory Usage  Execution Time  etc    Added  Is there a quantitative way of testing performance in JavaScript besides just perception of how fast the code runs

User · Answer

I have a small tool where I can quickly run small test-cases in the browser and immediately get the results:

JavaScript Speed Test

You can play with code and find out which technique is better in the tested browser.

User · Answer

I think JavaScript performance  time  testing is quite enough  I found a very handy article about JavaScript performance testing here

User · Answer

This is a good way of collecting performance information for the specific operation   start   new Date   getTime     for  var n   0  n  lt  maxCount  n         perform the operation to be measured       elapsed   new Date   getTime   - start  assert true  Measured time      elapsed

User · Answer

Profilers are definitely a good way to get numbers  but in my experience  perceived performance is all that matters to the user client  For example  we had a project with an Ext accordion that expanded to show some data and then a few nested Ext grids   Everything was actually rendering pretty fast  no single operation took a long time  there was just a lot of information being rendered all at once  so it felt slow to the user     We  fixed  this  not by switching to a faster component  or optimizing some method  but by rendering the data first  then rendering the grids with a setTimeout  So  the information appeared first  then the grids would pop into place a second later  Overall  it took slightly more processing time to do it that way  but to the user  the perceived performance was improved     These days  the Chrome profiler and other tools are universally available and easy to use  as are console time    console profile    and performance now    Chrome also gives you a timeline view which can show you what is killing your frame rate  where the user might be waiting  etc   Finding documentation for all these tools is really easy  you don t need an SO answer for that  7 years later  I ll still repeat the advice of my original answer and point out that you can have slow code run forever where a user won t notice it  and pretty fast code running where they do  and they will complain about the pretty fast code not being fast enough  Or that your request to your server API took 220ms  Or something else like that  The point remains that if you take a profiler out and go looking for work to do  you will find it  but it may not be the work your users need

User · Answer

I usually just test javascript performance  how long script runs  jQuery Lover gave a good article link for testing javascript code performance  but the article only shows how to test how long your javascript code runs  I would also recommend reading article called  5 tips on improving your jQuery code while working with huge data sets

User · Answer

You could use https   github com anywhichway benchtest which wraps existing Mocha unit tests with performance tests

User · Answer

I was looking something similar but found this   https   jsbench me   It allows a side to side comparison and you can then also share the results

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JSLitmus is a lightweight tool for creating ad-hoc JavaScript benchmark tests  Let examine the performance between function expression and function constructor    lt script src  JSLitmus js  gt  lt  script gt   lt script gt   JSLitmus test  new Function        function          return new Function  for var i 0  i lt 100  i                JSLitmus test  function         function             return  function     for var i 0  i lt 100  i                  lt  script gt    What I did above is create a function expression and function constructor performing same operation  The result is as follows   FireFox Performance Result    IE Performance Result

User · Answer

I think JavaScript performance  time  testing is quite enough  I found a very handy article about JavaScript performance testing here

User · Answer

Quick answer  On jQuery  more specifically on Sizzle   we use this  checkout master and open speed index html on your browser   which in turn uses benchmark js  This is used to performance test the library   Long answer  If the reader doesn t know the difference between benchmark  workload and profilers  first read some performance testing foundations on the  readme 1st  section of spec org  This is for system testing  but understanding this foundations will help JS perf testing as well  Some highlights      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    Performance testing JS  Ideally  the best perf test would be using your own application with your own workload switching what you need to test  different libraries  machines  etc   If this is not feasible  and usually it is not   The first important step  define your workload  It should reflect your application s workload  In this talk  Vyacheslav Egorov talks about shitty workloads you should avoid   Then  you could use tools like benchmark js to assist you collect metrics  usually speed or throughput  On Sizzle  we re interested in comparing how fixes or changes affect the systemic performance of the library   If something is performing really bad  your next step is to look for bottlenecks   How do I find bottlenecks  Profilers  What is the best way to profile javascript execution

User · Answer

You could use console profile in firebug

User · Answer

We can always measure time taken by any function by simple date object   var start    new Date        log start timestamp function1    var end     new Date        log end timestamp var diff   end - start

User · Answer

UX Profiler approaches this problem from user perspective  It groups all the browser events  network activity etc caused by some user action  click  and takes into consideration all the aspects like latency  timeouts etc

User · Answer

Here is a reusable class for time performance  Example is included in code           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

User · Answer

Here is a simple function that displays the execution time of a passed in function   var perf   function testName  fn        var startTime   new Date   getTime        fn        var endTime   new Date   getTime        console log testName           endTime - startTime     ms

User · Answer

Some people are suggesting specific plug-ins and or browsers  I would not because they re only really useful for that one platform  a test run on Firefox will not translate accurately to IE7  Considering 99 999999  of sites have more than one browser visit them  you need to check performance on all the popular platforms   My suggestion would be to keep this in the JS  Create a benchmarking page with all your JS test on and time the execution  You could even have it AJAX-post the results back to you to keep it fully automated   Then just rinse and repeat over different platforms

User · Answer

Performance testing became something of a buzzword as of late but that   s not to say that performance testing is not an important process in QA or even after the product has shipped  And while I develop the app I use many different tools  some of them mentioned above like the chrome Profiler I usually look at a SaaS or something opensource that I can get going and forget about it until I get that alert saying that something went belly up   There are lots of awesome tools that will help you keep an eye on performance without having you jump through hoops just to get some basics alerts set up  Here are a few that I think are worth checking out for yourself    Sematext com  Datadog com Uptime com Smartbear com Solarwinds com   To try and paint a clearer picture  here is a little tutorial on how to set up monitoring for a react application

User · Answer

You could use this  http   getfirebug com js html  It has a profiler for JavaScript

User · Answer

performance mark  Chrome 87    performance mark  initSelect - start    initSelect    performance mark  initSelect - end

User · Answer

I do agree that perceived performance is really all that matters  But sometimes I just want to find out which method of doing something is faster  Sometimes the difference is HUGE and worth knowing  You could just use javascript timers  But I typically get much more consistent results using the native Chrome  now also in Firefox and Safari  devTool methods console time    amp  console timeEnd   Example of how I use it  var iterations   1000000  console time  Function  1    for var i   0  i  lt  iterations  i          functionOne       console timeEnd  Function  1    console time  Function  2    for var i   0  i  lt  iterations  i          functionTwo       console timeEnd  Function  2     Update  4 4 2016   Chrome canary recently added Line Level Profiling the dev tools sources tab which let s you see exactly how long each line took to execute

User · Answer

Most browsers are now implementing high resolution timing in performance now    It s superior to new Date   for performance testing because it operates independently from the system clock   Usage  var start   performance now        code being timed     var duration   performance now   - start    References   https   developer mozilla org en-US docs Web API Performance now   http   www w3 org TR hr-time  dom-performance-now

User · Answer

I find execution time to be the best measure

User · Answer

Try jsPerf  It s an online javascript performance tool for benchmarking and comparing snippets of code  I use it all the time

User · Answer

The golden rule is to NOT under ANY circumstances lock your users browser  After that  I usually look at execution time  followed by memory usage  unless you re doing something crazy  in which case it could be a higher priority

[javascript] How do you performance test JavaScript code?

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