Is there a way to slow down browser DOM rendering and JS execution for development so we can see which parts of the website are too JS intensive and might be slow on slower machines? Maybe an extension for Chrome/Firefox for Linux/OSX?
Some clarification:
It's not about connection or testing the speed of the browser! It's just for our developers to see which parts of the page are rendered slowly or are "glitchy". For example when you use ajax and you are loading something you show a loader, but just after the loader is shown the loaded part is shown too. We want to see that in slow motion. Like when you press SHIFT in OSX when doing Expose.
PS. I did find some articles on delaying Internet connection, but that's not enough in this case.
PPS. Loading everything in VMs didn't work for us.
PPPS. Using slow down code like proposed in Javascript code for making my browser slow down is not the best option in my opinion.
Converting what #z0r said in the comments to an answer:
In Chrome, open devtools and select the Performance tab
Make sure Screenshots is checked
Press the record button (or hit Ctrl + E)
Do your activity
Stop recording
Hover over the timeline to see the screenshots of the screen as things change.
Use the timeline or profiler on your browser inspector. Here you can see, what functions take down the speed.
The accepted answer is good; I use and recommend Chrome Dev Tools as well.
As an alternative to Chrome Dev Tools:
Several 'website performance analysis' services offer timeline views. Run some internet searches and you'll find various free and paid options.
Try webpagetest.org
It's open source, highly regarded and has been running for years. It may offer different information, or is accessible in a different way, than Chrome Dev Tools.
In the test results, click "Filmstrip View".
Related
I have a very large javascript application, which contains mostly asm.js code (it's built upon urho3d c++ engine which is them compiled into asm.js).
It runs great on most browsers (chrome, firefox, safari, edge) but is extremely slow on IE11. The thing is, it is only slow until you open developer tools. With developer tools open, IE11 becomes ~10 times faster and is almost as fast as other browsers.
Here is a minimal example that reproduces the issue:
http://test.sebbia.com/urho3d/test.html
Open the page in any working browser, the time between "Run - start" message and "Run - finish" message should be around 1-2 seconds.
Open the page in IE11 without developer tools, time should be around 35-50 seconds.
Open developer tools and reload, time should be around 2-3 seconds.
Another important note is that if I start profiling session in developer tools, performance drops like if developer tools were closed. So I can actually profile the problem. But I've spent several hours profiling and I've tried inserting log messages in big functions but I haven't found no bottleneck. All functions take roughly the same time to execute and if I insert log message in a middle of a big functions, they'll usually break into 2 similar parts. So there is no single function that is responsible for slowdown, the code execution is just slow. Bit shifts, functions calls, arithmetic operations - it seems like they all just take way too much time compared to open developer tools.
I really need to make my app work on IE11 and the fact that it works with developer tools open drives me crazy. I'm trying to find a way to make IE think that tools are open even when they are not, or achieve good performance by any other means. So my questions is how can I achieve performance equal to IE11 with developer tools open without actually manually opening the tools?
This is a very broad question so I'd like to break it down into several smaller questions:
Is there a way to make IE11 think developer tools are open? Maybe there is something like x-ua-compatible meta tag I am missing?
What's causing the slowdown when developer tools are closed? I've heard that console.log function calls are slow without developer tools on IE8 and 9, maybe there is a similar thing on IE11? Maybe asm.js is not optimized? If I knew what's causing this I could at least try to rewrite code to avoid this.
Is there a way to open developer tools from javascript code? Maybe I could ask users to press a button on website to "make app faster". Asking them to press F12 or navigate settings seems too much.
When the debugger is enabled, asm.js compilation will be disabled and execution will fallback to be executed as normal JS - you can see the console.logs along these lines at the start of execution.
asm.js has been disabled as the script debugger is connected. Disconnect the debugger to enable asm.js. in Edge,
asm.js type error: Disabled by debugger in Firefox,
whilst Chrome will simply not open 01_HelloWorld.js in the debugger when you attempt to.
Disabling the debugger in IE (debugger tab, socket symbol; eighth from the left), and thus enabling asm.js will allow you to have dev tools open but see the slower execution. I have a horrible feeling that the slowdown when the debugger is closed is actually just IE11's speed issues with asm.js's optimisations.
There are a lot of references to IE11 being poorly optimised for asm.js. caniuse.com goes as far as listing IE11 as not supporting asm.js at all.
https://caniuse.com/#feat=asmjs
This appears to be backed up by Microsoft themselves:
https://developer.microsoft.com/en-us/microsoft-edge/platform/status/asmjs/
There would certainly appear to be some support for it, though clearly it has a number of speed issues as demonstrated in a number of benchmarks, for instance:
https://github.com/Kukunin/asm.js-benchmark/blob/master/README.md
Which shows IE11 around 10x slower than other browsers, or:
https://www.ghacks.net/2014/11/03/massive-benchmark-highlights-asm-js-performance-of-web-browsers/
Which is based on:
https://kripken.github.io/Massive/ - You can try it for yourself.
And many others. It may simply be that the IE11 implementation of asm.js is so poor that it is considerably slower with it, than without it.
EDIT: Added Microsoft platform status link.
There are two workaround for this issue:
to add setInterval(30000, () => {}) to your initialization function;
add MutationObserver=null to the beginning of the main html
You can also reference the discussion here:
https://github.com/OfficeDev/office-js/issues/521
This is just a guess but I had a similar problem in react-native then I found out about this:
When debugging remotely, your js bundle is using chrome's JSC and when
running on a device it's using the JSC provided by Apple on your phone.
Make sure that urho3d is not changing environment when developer tools are on/off.
Is there a way to remotely debug a website?
I've just finished putting together a website that has some jquery animations. The site works fine on every machine/configuration I've tested it on.
One of the people the site needs to work for, however, reports that the animations don't work; which effectively breaks the website.
I strongly suspect his companies' network is the root of the problem; however diagnosing this is challenging as he is not a technical user and guiding him through the webkit inspector/console, etc. is not really an option.
Ideally I'd like to be able to 'capture' the network/javascript logs from IE or Chrome so that I can inspect them and attempt to work out what's gone wrong.
Aside:
I'm using an off-the-shelf Wordpress theme (http://theme.co/x/) for the site; so I expect the code is good.
While it doesn't seem possible to remotely capture and inspect the network or javascript logs from another machine's browser; there are a number of services that allow you to add automatic error reporting to your javascript code, which you can then inspect to find the root of the problem.
Examples of these are Errorception and Raygun.
As far as I have found, there aren't any similar tools to do so for monitoring network performance / loading specifically- although a similar approach with a custom script to detect if specific items have been loaded could be written.
I have a large, javascript heavy web app that I am working on. I am experiencing very slow response times from Chrome Dev Tools for XHR responses and console loggging (3-5 secs). The actual app is running fast and responsive, only dev tools looks like it is suffering.
Does anyone have any idea why Chrome Dev Tools is becoming sluggish as my app grows?
Devtools are like any other debugger; they hook into the normal processing flow of an application, and store quite a bit more information than is normally required. This is much more work than simply rendering the page without debugging enabled, so it will indeed be slower.
That said, 3 seconds to respond to console.log seems high. I'd suggest that you first test the application in a nightly version of WebKit. If it's responsive in WebKit, but not in Chrome, please file a bug against the inspector via http://new.crbug.com/ along with any information you can provide about what scenario causes the slowness.
If it's equally sluggish in WebKit, please file a bug against WebKit's Inspector component: https://bugs.webkit.org/enter_bug.cgi
Either way, post the bug ID here, and I'll see that it's triaged into the correct team.
I "fixed" the slow chrome developer tool by (under SOURCES tab)
clearing the "watch" list that accumulated over time...
clearing all the "snippets", i had dozens as well...
Not sure which of both made the most difference, but it certainly made a difference
This is an old question, but it may help someone landing here later like I did.
Using Chrome 46.x/47.x on Linux (RHEL 7), none of the proposed solutions worked for me. What did work was to disable the setting "Use hardware acceleration when available", in the advanced browser settings.
I noticed in the process monitor/list that the Chrome renderer was taking up a lot of CPU, even putting a breakpoint or stepping throught statements in the debugger would take 10+ seconds!
Might be worth a shot.
Undock the developer tools into separate window.
In my case, it's work.
I struggled with this also, to the point where stepping through code using the chrome debugger was just so slow it took hours away from my productive development time. In watching the CPU utilization when debugging in chrome I would see it use up to as much at 40% of all 4 cores of my processor. I tried everything to no avail. Finally, I tried making the browser window of the page I was debugging as small as I could without losing any of the required view and miraculously it solved the problem. So, now I keep my debugger window popped out in a separate window, and make the window of the page I am debugging as small as I can and my debugging experience is very fast again. I have tested this over a period of weeks and it has held out. Hope this helps someone.
I've lately been running into odd issues, which I'm starting to think are related to resource starvation in the browser.
In FF:
I'd been testing one of our web apps and suddenly things that should disappear after a couple seconds stopped disappearing. I tracked back to setTimeout just flat out refusing to work. After reloading the browser it was all clear, no issues.
In IE:
I regularly see issues where IE will refuse to do transparency all the sudden, simply reloading the page clears this up.
In both:
Though I can't say its related for sure, I see unexplainable behavior, things along the lines of variables not being available (undefined) when they should be.
Both browsers also show a steady increase in memory usage over time (memory leaks).
The javascript in the web app is heavy and it is a single load page (making those memory issues mentioned all the more painful). There are lots of in-efficiency, and various things that make one say "why would you do that?".
Has anyone encountered such things? Can you point out general resources that will help identify and resolve these issues?
You could try running your application against the Chrome Profiler http://code.google.com/chrome/devtools/docs/overview.html. You can profile the CPU and get snapshots of the browser heap, that should help locate any rogue stuff.
If your application is designed to work with the Internet Explorer: The Developer Toolbar also has a profiler.
After an hour or two of heavy use on the site I'm developing, Firebug develops the following problems:
Breakpoints get glitchy -- it becomes difficult to add/remove breakpoints. Sometimes I click on a line multiple times, see nothing, move to the console tab and back, and then see my breakpoints again.
Console stops logging xhr's, or stops logging debug statements.
Script files become non-viewable.
I'm working with a javascript file which is quite large (over 10k lines). I don't think this is a memory leak issue with my own code. I'm refreshing the page all the time. Looks like an issue on the Firebug side. Is my logic sound? Is there anything I can do to get firebug to behave better? Or do I just need to restart firefox every hour?
Keep in mind Firefox while wonderful has always had many issues with handling memory. You should take a look at your task manager to see Firefox's memory footprint. Additionally I'd break up that JS file if you could into smaller chunks (for many reasons aside of this as well) to be better readable and work with the segments. Finally turn off plugins your not using or that may conflict with Friebug if your not using them.
I spent hours using Firebug without restart Firefox and never crashed, try a clean profile, install on it only Firebug and check if all works fine.
I use a separated development profile with Firebug and other dev oriented extensions installed.
How to configure a profile is described in many sites, on my wiki you find a brief description
i have similar problems! i think it is partially to do with the massive JS files. I just re-start firefox every once and a while. no big deal.