For...of Loops Often Beat reduce() in Readability, Debugging, and Performance

JavaScript developers frequently default to reduce() for array transformations, but the method is not always the best tool for the job. Simple for...of loops often require less cognitive effort to read and understand, especially for tasks like building lookup tables or filtering items. Many reduce() implementations also mutate the accumulator internally, undermining the functional-purity argument often cited in their favor. Spreading values into a new array on each iteration, a common reduce pattern, can be costly on large datasets. The key takeaway is that reduce() excels in specific cases like summing values or managing state, but a plain loop is frequently the clearer and faster engineering choice.