Javascript Chunk Array according to subArray length

Question

I have a problem about chunking subarrays. As you see below, there are many òbject inside detail. I want to split them if detail[i].length + detail[i+1].length >= 11 chunk array with 2, else chunk 3.

const isQuestions = 
  [ { question: ['ques 1?'], detail: [ {a:1}, {a:2}, {a:3}, {a:4}, {a:5}, {a:6} ] } 
  , { question: ['ques 2'],  detail: [ {b:1}, {b:2}, {b:3}, {b:4}, {b:5}, {b:6}, {b:7}, {b:8} ] } 
  , { question: ['ques 3?'], detail: [ {c:1}, {c:2}, {c:3}, {c:4}, {c:5}, {c:6}, {c:7} ] } 
  , { question: ['ques 4'],  detail: [ {d:1}, {d:2}, {d:3}, {d:4} ] } 
  , { question: ['ques 5'],  detail: [ {e:1}, {e:2}, {e:3}, {e:4} ] } 
  , { question: ['ques 6'],  detail: [ {f:1}, {f:2}, {f:3}, {f:4} ] }
  , { question: ['ques 7'],  detail: [ {g:1}, {g:2}, {g:3}, {g:4} ] } 
  ]

Expected array be like;

[ [ { question: ['ques 1?'], detail: [ {a:1}, {a:2}, {a:3}, {a:4}, {a:5}, {a:6} ] }
  , { question: ['ques 2'],  detail: [ {b:1}, {b:2}, {b:3}, {b:4}, {b:5}, {b:6}, {b:7}, {b:8} ] } 
  ]
, [ { question: ['ques 3?'], detail: [ {c:1}, {c:2}, {c:3}, {c:4}, {c:5}, {c:6}, {c:7} ] }
  , { question: ['ques 4'],  detail: [ {d:1}, {d:2}, {d:3}, {d:4} ] } 
  ]
, [ { question: ['ques 5'],  detail: [ {e:1}, {e:2}, {e:3}, {e:4} ] }
  , { question: ['ques 6'],  detail: [ {f:1}, {f:2}, {f:3}, {f:4} ] }
  , { question: ['ques 7'],  detail: [ {g:1}, {g:2}, {g:3}, {g:4} ] } 
] ]

As you see above, the sum of expected array's last part is 12. But It does not matter, the important thing is arr[i] + arr[i+1] length.

I did a function like inside map function. Because I have multiple array like this.

function isApsChunk(rawArray, size) {
    var returnedArray = [];
    for (var i = 0; i < rawArray.length; i += size) {
        if (rawArray[i + 1])
            if (rawArray[i].detail.length + rawArray[i + 1].detail.length >= 11) {
                returnedArray.push(rawArray.slice(i, i + 2));
            } else {
                returnedArray.push(rawArray.slice(i, i + size));
            }
    }
    return [returnedArray];
}
console.log(isApsChunk(isQuestions, 3))

But the problem is that function takes array with the length 7, gives me 5.

@MisterJojo it has something like that you mentioned. But it is not important, just you think Object.length — Kobayashi
– Kobayashi, Commented Nov 17, 2021 at 15:06

Mister Jojo · Accepted Answer · 2021-11-17 16:22:31Z

1

this way:
with the help of Array.reduce()

in this code the argument r (acronym of result [accumulator in doc MDN]) is initialized as follows:
r = {resp: [], blk: null, len: 0, count: 0}

r.resp becomes the final accumulator
r.blk points to the sub array to fill
r.len = size of the accumulation of arr detail
r.count = r.blk.length, linearity here has 3 by the size argument of the function

{[i + 1]: next} allows to point to the element i + 1 and name it next, they guess undefined when it is outside the array (when we are on the last element, the next one does not exist and !!next become false

!!next is equivalent to Boolean(next)

const isQuestions = 
  [ { question: ['ques 1?'], detail: [ {a:1}, {a:2}, {a:3}, {a:4}, {a:5}, {a:6} ] } 
  , { question: ['ques 2'],  detail: [ {b:1}, {b:2}, {b:3}, {b:4}, {b:5}, {b:6}, {b:7}, {b:8} ] } 
  , { question: ['ques 3?'], detail: [ {c:1}, {c:2}, {c:3}, {c:4}, {c:5}, {c:6}, {c:7} ] } 
  , { question: ['ques 4'],  detail: [ {d:1}, {d:2}, {d:3}, {d:4} ] } 
  , { question: ['ques 5'],  detail: [ {e:1}, {e:2}, {e:3}, {e:4} ] } 
  , { question: ['ques 6'],  detail: [ {f:1}, {f:2}, {f:3}, {f:4} ] }
  , { question: ['ques 7'],  detail: [ {g:1}, {g:2}, {g:3}, {g:4} ] } 
  ]  

const isApsChunk = (rawArray, size) => 
  rawArray.reduce((r,elm,i,{[i+1]:next}) =>
  {
  if (r.len===0 || r.len >= 11 || r.count >= size)
    {
    r.len   = 0
    r.count = 0
    r.blk   = []
    r.resp.push(r.blk )
    }
  r.len += elm.detail.length
  r.count++
  r.blk.push( elm )

  return (!!next)?r:r.resp
  },{ resp:[], blk:null, len:0, count:0 } )
  
console.log(  isApsChunk(isQuestions, 3) )

.as-console-wrapper { max-height: 100% !important; top: 0 }

edited Nov 17, 2021 at 16:22

answered Nov 17, 2021 at 15:06

Mister Jojo

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2 Comments

Kobayashi Over a year ago

Can you add some comment blocks for more understanding, please?

Mister Jojo Over a year ago

@apsisx I added some explanations, need more ?

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