Benchmark JavaScript forEach versus for loops online with realistic data, shareable jsPerf results, and browser plus runtime performance analysis.
A fair iteration benchmark compares equivalent work.
Generate the array in setup so allocation does not dominate every test case.
Have both implementations produce the same result so dead-code elimination is less likely to distort the result.
Try small, medium, and large input sizes if your production workload varies.
Iteration benchmarks are easy to make misleading.
Do not compare a loop that does less work with a callback that does more work.
Do not generalize one browser result to every runtime and hardware profile.
Do not trade away readability unless the benchmark maps to a real hot path.
Short answers for searchers, with enough context to help them create a better benchmark.
It often can be slower for hot array loops because each iteration goes through a callback, but the real answer depends on the workload, runtime, input size, and surrounding code.
No. Use readable code by default. Consider a for loop when the measured difference matters for a real performance-sensitive path.
Use the same input array, put data generation in setup, make both test cases perform equivalent work, and rerun the benchmark in the environments you care about.
Yes. Browser results are available directly, and Deep Analysis plus the optional worker can add QuickJS, V8, Node, Deno, and Bun signals.
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