"Anti-pattern" sounds close enough, as shorthand, when "bug" might cause readers to file the article incorrectly. The author is warning others that a normally-unremarkable JavaScript idiom causes suboptimal performance in this particular case, and it's likely not to present itself as a bug (having no visible symptoms on smaller pages and no impact on functionality otherwise). Putting aside whether suboptimal performance should always be classified as a bug, there are many ways to accidentally break equality comparisons (despite a full understanding of them), and now my eyes are primed to catch one more pitfall. I appreciate when that happens for reason that doesn't involve hard experience.