Convert array of objects to array of arrays (by attribute)

Question

I want transform my array to array of arrays by attribute "icon".

const array = [
  { icon: true }, 
  { icon: false },
  { icon: false }, 
  { icon: true }, 
  { icon: false }
]

I need:

[[{icon: true}, {icon: false}, {icon: false}], [{{icon: true}, {icon: false}}]]

Attribute icon === true is a sign of the beginning of the formation of a new array.

I think you should use the function reduce.

array.reduce((result, item, index) => { ... }, [])

How best to write a transformation? Thanks!

please add what **you** have tried. – Nina Scholz Jan 10 '19 at 12:20 — Nina Scholz, Jan 10 '19 at 12:20

Mohammad Usman · Answer 1 · 2019-01-10T12:35:34.443

4

You can use .reduce() method as follow:

const data = [{ icon: true }, { icon: false }, { icon: false }, { icon: true }, { icon: false }]

const result = data.reduce((r, c) => {
  if(c.icon === true)
    r.push([c]);
  else
    r[Math.max(r.length - 1, 0)].push(c);
    
  return r;
},[]);

console.log(result);

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edited Jan 10 '19 at 12:35

answered Jan 10 '19 at 12:23

Mohammad Usman

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Thanks! It is perfectly! – user3468894 Jan 10 '19 at 12:26

score 0 · Answer 2 · answered Jan 10 '19 at 12:34

You could use a while loop.

const array = [{ icon: true }, { icon: false }, { icon: false }, { icon: true }, { icon: false }]
i = 0;
result = [];
aux = [];
while(i <  array.length){
   if(array[i].icon){
     if(aux.length !== 0){
        result.push(aux);
        aux = [array[i]];
     }
     else
        aux.push(array[i]);
   }
   else
     aux.push(array[i]);
   i++;
}
result.push(aux);
console.log(result);

score 0 · Answer 3 · answered Jan 10 '19 at 12:58

You could use a closure over the array for inserting. This prevents to look up the last item in the array.

const
    data = [{ icon: true }, { icon: false }, { icon: false }, { icon: true }, { icon: false }],
    result = data.reduce((a => (r, o) => {
        if (o.icon) r.push(a = []);
        a.push(o);
        return r;
    })(), []);

console.log(result);

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

Abdulsalam Ayinla · Answer 4 · 2019-01-11T03:21:48.833

const array = [
  { icon: true },
  { icon: false },
  { icon: false },
  { icon: true },
  { icon: false }
];

console.log(grouper(array));

function grouper(array) {
  return array.reduce((acc, next) => {
    const entry = [next];

    if (next.icon) return acc.concat([entry]);
    const beforeNextCollection = acc.slice(0, acc.length - 1);

    const nextCollection = acc[acc.length - 1];
    const updatedCollection = nextCollection.concat(entry);

    return beforeNextCollection.concat([updatedCollection]);
  }, []);
}

Convert array of objects to array of arrays (by attribute)

4 Answers4