Agreed, and issues like this make me hugely suspicious of JS performance benchmarks. I'm only familiar with V8, but my experience has been that there are more o

Agreed, and issues like this make me hugely suspicious of JS performance benchmarks. I'm only familiar with V8, but my experience has been that there are more or less three "tiers" of factors that affect performance: 1. whether the optimizing compiler gets used 2. random stuff that's impossible to know about unless you grab your code's internal representation and decompile it [1] 3. the raw performance of individual statements The effects of (1) dominate (2), and the effects of (2) dominate (3). So when I see performance micro-benchmarks that purport to measure (3) without apparently paying any attention to (1) or (2), my first inclination is to assume the results are essentially random noise. [1] E.g. whether statements get wrapped in type checks, whether an integer variable gets handled internally as a SMI (small int) or whether it keeps getting converted to a boxed Number and back. The cost of such things can easily exceed the cost of the statement you're trying to benchmark.