Good developers should know how the code works and choose the best solution in every situation.ĭeclarative programming, with its simplicity, wins most of the time. We’ve also confirmed that destructuring is free and should be used whenever it’s convenient. Pre-allocating an array of known length is much faster than relying on dynamic growth with push. V8 already does a great job and probably even eliminates the boundary checks as well. Micro-optimizations of the for loop don’t make sense for arrays in JavaScript. There’s not much performance difference between the two loops, and you can use whatever better fit’s the algorithm. forEach is almost the same as for or for.of, only slower. Imperative code is a lot more verbose in most cases.įive code lines for a simple sum are too much, and reduce is just a one-liner. Invoking callback function is not free and adds up for big arrays.įor more complex code than a simple sum, however, there won’t be that much of a relative difference,Īs the calculations themselves would take more time. The benchmarks proved that imperative programming with loops results in better performance than using convenient Array methods. The tests again showed no difference between the loops. So unless the performance is that critical. Writing that many code lines for just a simple sum must have a strong reason, Input for the tests was an array of one million objects with the structure return result The test application uses the benchmark library to get statistically significant results. We would love your feedback and contributions! Still, when processing large amounts of data in some business intelligence app, video processing, scientific calculations, or game engine, this will have a massive effect on the overall performance. It doesn’t add up to a significant difference in most applications. Loops are usually three or more times faster than their declarative counterparts. It’s better 99% of the time, but not when performance matters. forEach Array methods over simple loops in JavaScript?”ĭeclarative programming style is very expressive, easier to write, and far more readable. While we partially agree, that got us thinking: He explained that he writes only declarative code, and there’s no point in imperative programming anymore. Once, we interviewed a mid-developer position candidate that couldn’t answer a simple question involving the while loop.

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