How to find the count of some object property in array of objects using react and javascript?

Question

Hi below is the array of objects.

const arr_obj = [
    {
        id: '1',
        children: [],
        type: 'TYPE1',
     },
     {
         id: '2',
         children: [
             {
                 id: '1',
                 children: [
                     {
                          //some attributes
                     }
                 ],
                 type: 'MAIN',
             },
             {
                 id: '2',
                 children: [
                     {
                         //some attributes
                     }
                 ],
                 type: 'MAIN',
             },
             {
                 id: '3',
                 children: [
                     {
                         //some attributes
                     }
                 ],
                 type: 'MAIN',
             },
         ]
         type: 'TYPE2',
     },
     {
         id: '3',
         children: [
             {
                 id: '4',
                 children: [
                     {
                         //some attributes
                     }
                 ],
                 type: 'MAIN',
             },
             {
                 id: '5',
                 children: [
                     {
                         //some attributes
                     }
                 ],
                 type: 'MAIN',
             },
             {
                 id: '6',
                 children: [
                     {
                         //some attributes
                     }
                 ],
                 type: 'MAIN',
             },
         ]
         type: 'TYPE2',
     }
 ]

I have to find out the count of type: 'MAIN'. these 'MAIN' will be within type: "type2"

So the expected count is 6. The outer children array can be empty and sometimes inner children array with type: "type2" is not there at all examples like below:

children: [] //empty array


children: [
    {
        id: '1',
        children: [],
        type: 'TYPE2',
    },
] //no children with type: 'TYPE2'

below is the code to handle above,

const findCount = (arr_obj) => {
  let count = 0;
  const expectedCount = 2;
  const loop = (children) => {
    for (const obj of children) {
      const { type, children } = obj;
      if (type === 'TYPE2') {
        loop(children);
      } else if (type === 'MAIN') {
        ++count;
      }
    }
  };
  loop(children);
  return count > expectedCount;
};

const output = findCount(arr_obj);

the above works fine. but it doesnt handle case when inner children is [] like below,

children: [
    {
        id: '1',
        children: [],
        type: 'TYPE2',
    },
 ] //no children for type: 'TYPE2'

how can i handle the above data with no inner children array for children of type "TYPE2". could someone help me with this. thanks.

For inspirational purposes, here is another way to count the "MAIN" nodes: gist.github.com/3limin4t0r/88e6069deda346fe9540b02063a959c4 This doesn't address the issue in the question, so I wont post it as an answer. — 3limin4t0r
– 3limin4t0r, Commented Jan 12, 2022 at 11:41

3limin4t0r · Accepted Answer · 2022-01-10 13:54:00Z

1

how can i handle the above data with no inner children array for children of type "TYPE2".

You could add a guard clause to your loop function:

if (!children) return;

Which returns directly if there are no children.

Resulting in:

const findCount = (arr_obj) => {
  let count = 0;
  const expectedCount = 2;
  const loop = (children) => {
    if (!children) return;

    for (const obj of children) {
      const { type, children } = obj;
      if (type === 'TYPE2') {
        loop(children);
      } else if (type === 'MAIN') {
        ++count;
      }
    }
  };
  loop(arr_obj); // <- this should probably refer to `arr_obj`
  return count > expectedCount;
};

const output = findCount(arr_obj);

answered Jan 10, 2022 at 13:54

3limin4t0r

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Comments

Akshay Mathur · Accepted Answer · 2022-01-10 13:47:03Z

0

For no inner children, you can check if the array of children has any elements in it or not. Something like this

const loop = (children) => {
  for (const obj of children) {
    const { type, children } = obj;
    if (type === 'TYPE2' && children.length > 0) {
      loop(children);
    } else if (type === 'MAIN') {
      ++count;
    }
  }
};

answered Jan 10, 2022 at 13:47

Akshay Mathur

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Comments

Ram Rana · Accepted Answer · 2022-01-10 14:05:33Z

0

    let count = 0;
    arr_obj.?.filter(item=> item.type =="TYPE2").forEach((item)=> {
if(item.children.length > 0){
    item.children.forEach((childItem)=>{
    if(childItem.type == "MAIN"){
count+=1;
}
    })
}
})
    console.log(count);// output will be 6

answered Jan 10, 2022 at 14:05

Ram Rana

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Comments

Amila Senadheera · Accepted Answer · 2022-01-10 14:19:48Z

I modified the example by adding another valid occurrence in the nested object.

The following would also work.

// count the occurences of typeX as the very next of typeY
const count_TypeX_Within_TypeY = (arr, typeX, typeY) => {
  let count = 0;
  arr.forEach((item) => {
    // check the type in current level
    if (item.type === typeY) {
      item.children.forEach((innerItem) => {
        // // check the type in next level
        if (innerItem.type === typeX) {
          count += 1;
        }
      });
    }
    // do the same recursively
    count += count_TypeX_Within_TypeY(item.children || [], typeX, typeY);
  });

  return count;
};

const arr_obj = [{"id":"1","children":[],"type":"TYPE1"},{"id":"2","children":[{"id":"1","children":[{}],"type":"MAIN"},{"id":"2","children":[{}],"type":"MAIN"},{"id":"3","children":[{}],"type":"MAIN"}],"type":"TYPE2"},{"id":"3","children":[{"id":"4","children":[{}],"type":"MAIN"},{"id":"5","children":[{"id":"7","type":"TYPE2","children":[{"id":"8","type":"MAIN","children":[{}]}]}],"type":"MAIN"},{"id":"6","children":[{}],"type":"MAIN"}],"type":"TYPE2"}];

console.log(count_TypeX_Within_TypeY(arr_obj, "MAIN", "TYPE2"));

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