score:1

Accepted answer

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);

score: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;
    }
  }
};

score: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

score:0

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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