Reduce is a good illustration of the principle of least power[1]: it's powerful, flexible, general and low-level and can technically achieve any combination of summation, map, filter, find/includes, some/any/every, etc. But reduce is misused if it's reimplementing patterns available in higher-level form.
In cases when reduce is required because (for example) JS doesn't have a sum function, it should be kept simple. `arr.reduce((acc, el) => el + acc, 0)` is acceptable if lodash _.sum() is not available.
In cases when reduce is required because the higher-level operations like map/filter aren't flexible enough, decompose the reduction operation into simpler steps and use map/filter with multiple passes, or write a traditional for..of loop.
This principle also explains why enhanced/range/of loops are preferred over counter-based `for` loops, and counter-based loops over `while`. Technically all loops can be handled by `while`, but it's seldom needed because enhanced loops handle the common case with the cleanest syntax. Reduce/while/counter-based `for` loops are antipatterns where higher-level, less powerful abstractions exists.
Chained filter and map don't necessarily iterate multiple times. They certainly can but depending on how things are built they very often run as a single loop with the operations chained.
ggorlen · · focus · HN ↗
In cases when reduce is required because (for example) JS doesn't have a sum function, it should be kept simple. `arr.reduce((acc, el) => el + acc, 0)` is acceptable if lodash _.sum() is not available.
In cases when reduce is required because the higher-level operations like map/filter aren't flexible enough, decompose the reduction operation into simpler steps and use map/filter with multiple passes, or write a traditional for..of loop.
This principle also explains why enhanced/range/of loops are preferred over counter-based `for` loops, and counter-based loops over `while`. Technically all loops can be handled by `while`, but it's seldom needed because enhanced loops handle the common case with the cleanest syntax. Reduce/while/counter-based `for` loops are antipatterns where higher-level, less powerful abstractions exists.
[1]: <a href="https://wiki.c2.com/?PrincipleOfLeastPower" rel="nofollow">https://wiki.c2.com/?PrincipleOfLeastPower
marcta · · focus · HN ↗
QuercusMax · · focus · HN ↗