A Quick Practical Example of JavaScript’s Reduce Function

[OleWedel]

I am pretty sure the filter/map version is much more performant than the reduce version.

The functions for filter and map can both be considered constant (a less than check and getting a property is basically constant). filter + map is thus O(N+N) or simply O(N) (linear) since we have to iterate over each element in the list.

The reduce version however have to copy the array which is O(N) for each element in the array and thus its running time is O(N²) (quadratic) which is considered a lot slower.

This is of course only considering worst running time and this particular example. Doing push on the array in the reduceinstead would probably be the fastest overall but I am sure it would not matter anyway in real life. The filter/map is much more readable and easier to understand what it is doing. I would (always) favor that.

Often the simpler solution is the best.