Performance degradation when CSS is loaded using XMLHttpRequest

[Matthew Reiter]

EQCSS uses the following code to load CSS from link tags:

              var xhr = new XMLHttpRequest

              xhr.open('GET', script[i].src, true)
              xhr.send(null)
              xhr.onreadystatechange = function() {

                EQCSS.process(xhr.responseText)

              }

Because it doesn't verify that the ready state is done, it repeatedly processes partial responses, resulting in duplicate queries getting added to EQCSS.data. This has a worse impact for IE than other browsers because IE calls onreadystatechange every 4 KB of data downloaded, whereas Firefox and Chrome call onreadystatechange less frequently.

The MDN documentation (https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/onreadystatechange) includes an example on how to use onreadystatechange that checks the ready state (and for good measure also verifies that the request was successful):

xhr.onreadystatechange = function () {
  if(xhr.readyState === 4 && xhr.status === 200) {
    console.log(xhr.responseText);
  }
};

When I tried putting in the ready state check it fixed the performance problems I was seeing.

[Tommy Hodgins]

Thanks for reporting this! I haven't noticed this, is there a specific test case where you know you can observe this happening so I can take a peek?

Thank you as well for the suggested fix too! Once I can reproduce and test it shouldn't take long to get a patch out. I really appreciate you opening this issue <3

[Matthew Reiter]

This would happen any time you have CSS referenced with a <link> tag and the linked CSS file is larger than 4 KB (the bigger it is, the worse the performance gets). I initially found the problem by putting a breakpoint in the browser debugger in the EQCSS.apply function and noticed that EQCSS.data had many duplicate entries.

[Matthew Reiter]

You could probably reproduce the problem by making style.eqcss much larger and then loading link.html.

[Tommy Hodgins]

Thanks! I'll see if I can reproduce this :3

[Tommy Hodgins]

Thank you so much for researching & reporting this, I was able to send out a new v1.9.1 release just now including your suggested fix!

Let me know if this solves it for you, and hope you have a wonderful weekend <3

[Matthew Reiter]

Thanks! I've confirmed that my problem is fixed in version 1.9.1.

[Tommy Hodgins]

Beautiful! Hope you have a wonderful week :3