Yes, after watching so many of Vyacheslav Egorov's (from V8) talks on microbenchmarking, I'm convinced that JIT's are doing some serious witchcraft unmeasurable

Yes, after watching so many of Vyacheslav Egorov's (from V8) talks on microbenchmarking, I'm convinced that JIT's are doing some serious witchcraft unmeasurable by microbenchmarks; yet googling relevant tests on jsperf is tough habit to shake off. As this example shows. While we are on the subject, can I ask if there are any performance advantages of using data attributes over custom attributes for storing data in an element? In other words, can adding non-standard attributes to an element cause any deoptimizations? I know that JS engines use hidden classes/object shapes to optimize JS objects, I assumed something similar might be the case for DOM elements, in that case adding non-standard attribute must mean deoptimization.