Reliably benchmarking optimizing VMs like Java and JavaScript is a research problem.

See “Virtual machine warmup blows hot and cold”. The authors run a variety of benchmarks (with a pristine methodology) and find 43% of them provide “bad inconsistent” results.

Paper summary: https://blog.acolyer.org/2017/11/07/virtual-machine-warmup-b...

Paper: https://dl.acm.org/doi/pdf/10.1145/3133876