[jandem]

SpiderMonkey dev here. Does this reproduce for you with a clean profile? Because I just tried this with 78.0b9 too and for the first one, Local (original), I get 6.7 ms in the Web Console, very similar to what I see in Chrome. I didn't look at the other ones.

[hmwhy]

Hello! Many apologies for having taken a while to reply, I finally found some time to sit down and do some tests because > 200 ms vs. < 10 ms is too big of a difference, and also because of what london_explore said:

> and if that performs badly, open a bug with V8 or other JavaScript engines to optimize it.

Anyhow! Just to clarify before moving on, I also did the tests in the Web Console. All numbers noted below are for the same (first) test I initially mentioned.

What I have done in exactly the same order as follows:

1. I first tested with a clean profile as you suggested and the times haven't changed. ~240 ms was observed.

2. I downloaded Firefox and tested with a clean installation of 77.0.1. ~240 ms was observed.

3. I removed both Firefox (77.0.1) and Firefox Developer edition (78.09b), and manually removed the ~/Library/Application Support/Firefox folder. I then reinstalled Firefox Developer edition (78.09b) and, without restoring my profiles, I tested again. ~240 ms was observed.

4. I re-ran exactly the same tests on NodeJS and Chrome. ~6 ms was observed.

Assuming that it's just me, I can't immediately think of what is causing this.

Otherwise, if it's not just my setup, could it be related to the operating system? I'm currently running macOS 10.15.5. I don't have a machine with a different OS that I can test on at the moment, I should be able to try this in the next 2 hours and will update this post.

Edit: I have tested on Windows 10 as well and the issue is the same!