[espadrine]

There are many cases of elegantly using reduce() with a different return type than the list's item type.

Here is a JS function which computes the combined length of all strings in a list:

    stringsLen = (strings) => strings.reduce((acc, item) => acc += item.length, 0);
    
    stringsLen(['hello', 'world'])  //> 10

Sure, you can argue that this works, but it misses the point.

    stringsLen = (strings) => strings.map(s => s.length).reduce((acc, n) => acc += n, 0);
    
     stringsLen(['hello', 'world'])