1

I have an "object of objects of arrays" and I simply need to get the total count of elements in the "bottom level" arrays ...so with the example below, I need to return 19 (counting elements a to s):

var arr={ 'AA': { 'aa': ['a','b'],
                  'bb': ['c','d'],
                  'cc': ['e','f'],
                  'dd': ['g','h'] }, 
          'BB': { 'ee': ['i','j'],
                  'ff': ['k','l'] }, 
          'CC': { 'gg': ['m','n'],
                  'hh': ['o','p'],
                  'ii': ['q','r','s'] } };

I have it working with this but it ain't pretty:

var cnt=0;
for(var f0 in arr){
  for(var f1 in arr[f0]){
    cnt+=arr[f0][f1].length;
  }
}

It's probably best to use map and reduce but can't quite wrap my head around it. There are similar Q+A's (like this) but I couldn't quite find one that fits this situation.

Thanks!

ashleedawg
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  • You can't use map or reduce on your datastructure, because this two functions are from the Array.prototype and your datastructe is an array in an object in an object as you stated correct. Or just for the inner arrays? so to replace that part --> cnt+=arr[f0][f1].length;? – grisuu May 18 '22 at 07:54

1 Answers1

1

By using Object.values to access the values associated with each key, you can use a nested reduce to count all the bottom level elements:

var arr={ 'AA': { 'aa': ['a','b'],
                  'bb': ['c','d'],
                  'cc': ['e','f'],
                  'dd': ['g','h'] }, 
          'BB': { 'ee': ['i','j'],
                  'ff': ['k','l'] }, 
          'CC': { 'gg': ['m','n'],
                  'hh': ['o','p'],
                  'ii': ['q','r','s'] } };
                  
const cnt = Object.values(arr)
  .reduce((c, o) => c + Object.values(o)
    .reduce((c, a) => c + a.length,
            0),
          0);
  
console.log(cnt)
Nick
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