[throwaway0asd]

QuerySelectors are slow. Epic slow. I would also argue that querySelectors are far less flexible and became popular because they are instead easy.

https://jsbench.github.io/#b39045cacae8d8c4a3ec044e538533dc

ProTip: Without numbers performance opinions are wrong by several orders of magnitude 80% of the time.

[wruza]

I’m getting 70mops byId and 23mops qs-#id. This looks like making a huge difference until I add these cases:

  3: "abc”.replace("a", "b")
  4: "1" * 2

Which result in 15mops and 74mops respectively. This test measures diameters of neutrinos so to say.

[throwaway0asd]

My experience is that most developers tend to guess at performance and throw away numbers they disagree with. As a result performance testing is only something product owners care about.