Modifying a specific value in a nested object (JavaScript)

Question

I got this type of object:

const obj = {
    group: {
        data: {
            data: [
                {
                    id: null,
                    value: 'someValue',
                    data: 'someData'
                }
            ]
        }
    }
};

I need to edit this object so whenever null is in the property value, it would be replaced with some string.

Meaning if the replacement string will be 'someId', the expected outcome is:

const obj = {
    group: {
        data: {
            data: [
                {
                    id: 'someId',
                    value: 'someValue',
                    data: 'someData'
                }
            ]
        }
    }
};

Closest I found were this and this but didn't manage to manipulate the solutions there to what i need.

How should I do it?

Would love to. This is what I'm getting from an API that's not under my control. — flow24, Mar 06 '22 at 18:29
try https://stackoverflow.com/a/52368116/13583510 instead of delete try setting `object[k]="some data"` — cmgchess, Mar 06 '22 at 18:38
Are you only needing to update the `id` values of `obj.group.data.data` or will there be other places to replace null? How will you know what the `id` value should be if you don't have it to begin with? This question needs more information. — PsiKai, Mar 06 '22 at 18:49

PsiKai · Answer 1 · 2022-03-07T02:39:01.363

Probably running into issues with the array values. Pass in the index of the array to modify. In this case [0]

obj.group.data.data[0].id = "someId"

EDIT This will update all null values of id inside the data array:

obj.group.data.data.forEach(o => {
  if (o.id === null) {
    o.id = "someId"
  }
})

Another EDIT

Here is an algorithm to recursively check all deeply nested values in an object. It will compile an array of object paths where null values live. There is an included helper method to find and update the value of the object at the given path in the array. There is a demonstration of the program in the console.

const object = {
  group: {
    data: {
      data: [
        {
          id: null,
          value: "foo",
          data: [null, "bar", [null, { stuff: null }]]
        },
        {
          id: null,
          value: null,
          data: {
            bar: [null]
          }
        },
        {
          id: null,
          value: "foo",
          data: null
        },
        {
          id: 4,
          value: "foo",
          data: "bar"
        },
        {
          id: 4,
          value: "stuff",
          data: null
        }
      ]
    },
    attributes: null,
    errors: ["stuff", null]
  }
}

const inspectProperty = (key, obj, path = "") => {
  if (typeof obj[key] === "object") {
    if (obj[key] instanceof Array) {
      return analyzeArray(obj[key], `${path ? path + "." : ""}${key}`);
    }
    return analyzeObj(obj[key], `${path ? path + "." : ""}${key}`);
  }
  return [];
};

const analyzeKey = (obj, key, path = "") => {
  if (obj[key] === null) return [`${path ? path + "." : ""}${key}`];
  return inspectProperty(key, obj, path).reduce((a, k) => [...a, ...k], []);
};

const analyzeObj = (obj, path = "") => {
  return Object.keys(obj).map((item) => analyzeKey(obj, item, path));
};

const analyzeArray = (array, path) => {
  return array.map((item, i) => analyzeKey(array, i, path));
};

const updateNullValue = (path, value) => {
  let p = path.split(".");
  p.reduce((accum, iter, i) => {
    if (i === p.length - 1) {
      accum[iter] = value;
      return object;
    }
    return accum[iter];
  }, object);
};

let nullValues = analyzeObj(object)[0]

console.log(nullValues)

nullValues.forEach((nullVal, i) => {
  updateNullValue(nullVal, "hello-" + i)
})

console.log(object)

Curious as to if and why this doesn't solve OPs issue. Would be good to know so I can modify to a more correct answer. — PsiKai, Mar 06 '22 at 18:35
i think there can be many places with nulls. so OP wants to dynamically change them — cmgchess, Mar 06 '22 at 18:37
Going to need more information from @flow24 then to get to the bottom of this. — PsiKai, Mar 06 '22 at 18:39
The guys above are right. I don't know how many (and where) `null` will be, this is just a static example. — flow24, Mar 06 '22 at 19:07
So how would you know what the null values needs to be if I can help you find them? Is that a requirement of the question, or do you just need to locate the null values? Is there anything else in the data structure, such as more nested keys, or is that unknown too? — PsiKai, Mar 06 '22 at 19:09
@flow24 I made one last edit for posterity. This will find all null values in an unknown object. — PsiKai, Mar 07 '22 at 02:40

Modifying a specific value in a nested object (JavaScript)

1 Answers1