How to keep only one object in a nested object inside an array

Question

I'm having an array look like this

 [
  { 
    object1:{ childObj1:[grandChild1,grandChild2], childObj1, childObj1}
  },
  { 
    object2:{ childObj1:[grandChild1,grandChild2], childObj1, childObj1}
  },
  { 
    object3:{ childObj1:[grandChild1,grandChild2], childObj1, childObj1}
  },

 ]

Now i want to get rid of every nested item that have more than one item and keep only the first, like :

 [
  { 
    object1:{ childObj1:[grandChild1]}
  },
  { 
    object2:{ childObj2:[grandChild1]}
  },
  { 
    object3:{ childObj3:[grandChild1]}
  },

 ]

Which is the most effective way to do this?

`object1:[ childObj1:[grandChild1]]`. `childObj1` in `[]` is not an object. I'm not sure how you define `childObj1` — Nick Vu, May 05 '22 at 03:37
Does this answer your question? [How can I access and process nested objects, arrays or JSON?](https://stackoverflow.com/questions/11922383/how-can-i-access-and-process-nested-objects-arrays-or-json) — Edwin, May 05 '22 at 05:11

A G · Answer 1 · 2022-05-05T04:58:48.903

const arr = [{
    object1: {
      childObj1: ['grandChild1', 'grandChild2'],
      childObj3: 't',
      childObj2: 'r'
    }
  },
  {
    object2: {
      childObj1: ['grandChild1', 'grandChild2'],
      childObj3: 't',
      childObj2: 'r'
    }
  },
  {
    object3: {
      childObj1: ['grandChild1', 'grandChild2'],
      childObj3: 't',
      childObj2: 'r'
    }
  },

];

console.log(arr.map(el => {
  const child = el[Object.keys(el)[0]];
  const firstProperty = {
    [Object.keys(child)[0]]: child[Object.keys(child)[0]]
  };
  return {
    [Object.keys(el)[0]]: firstProperty
  }
}));

Hope this is what you wanted.

@CODEforDREAM Do accept this as answer if it solves your issue. — A G, May 05 '22 at 07:46

Leon · Answer 2 · 2022-05-05T10:57:19.300

Try this:

const arr = [{
    object1: {
      childObj1: ['grandChild1', 'grandChild2'],
      childObj2: {},
      childObj3: {}
    }
  },
  {
    object2: {
      childObj1: ['grandChild1', 'grandChild2'],
      childObj2: {},
      childObj3: {}
    }
  },
  {
    object3: {
      childObj1: ['grandChild1', 'grandChild2'],
      childObj2: {},
      childObj3: {}
    }
  },
]

function f(obj, startLevel, currentLevel = 0) {
  let value
  if (Array.isArray(obj)) {
    value = []
  } else if (typeof obj === 'object') {
    value = {}
  } else {
    value = obj
  }

  if (typeof obj === 'object') {
    for (let i in obj) {
      if (currentLevel >= startLevel) {
        if (Array.isArray(obj[i])) {
          value[i] = obj[i].length ? [f(obj[i][0], startLevel, currentLevel + 1)] : [];
        } else {
          value[i] = f(obj[i], startLevel, currentLevel + 1)
        }
        break;
      } else {
        value[i] = f(obj[i], startLevel, currentLevel + 1)
      }
    }
  }

  return value;
}

console.log(f(arr, 1));

Thank for your answer, it work well but still have small problem, if the item contain multi object, it still have more than one value, i just want to keep one value of all object and array — CODEforDREAM, May 05 '22 at 07:32
I think you mean the left item should also be handled, and update the code, please try again, thanks! — Leon, May 05 '22 at 08:31

How to keep only one object in a nested object inside an array

2 Answers2