On every call to console.log() it looks like we call HS_regroupOutput. This ends up evaluating a fairly slow selector on everything in the console, then steps through everything in the console and twiddles its classes. This is one of the sources of the nodelist .length gets (one per loop iteration, instead of grabbing the length up front), and presumably the source of a lot of the .classList and class-changing stuff. If there's any way this could be coalesced across multiple log() calls, that would probably help a lot.
bz, thank you for the bug report! HS_regroupOutput() has been removed in bug 793996.
Status: NEW → RESOLVED
Last Resolved: 6 years ago
OS: Mac OS X → All
Hardware: x86 → All
Resolution: --- → FIXED
Whiteboard: [fixed by bug 793996]
Target Milestone: --- → Firefox 25
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