left-pad only adds 7ms on edge, seems worth it.
On the other hand, Jquery adds almost a second. And you hardly ever see pages that don't use it. (Unless they use some other heavy js library). But it's just soo convenient.
[0] http://www.adriancourreges.com/blog/2017/12/15/mgs-v-graphic...
7ms is hardly anything but apply it to a list of only a 1000 elements and you have now slowed down the user experience by 7000ms (I know, this would all be buffered and hidden, etc. but this is just one tiny component and eventually all this stuff leads to real perceptible awful jankiness that could have been avoided if people allowed themselves to think a bit about performance).