How to return the difference between two Objects having array and return the difference value dynamically

Question

Let's say I have two objects of arrays:

const newObj = {
      description: "abcd",
      type: "anything",
      list: [
        { id: 1, name: "Peter" },
        { id: 2, name: "Cathenna" },
        { id: 3, name: "Chiyo" }
      ]
    }

   const oldObj = {
      description: "wwew",
      type: "anything",
      list: [
        { id: 1, name: "Amara" },
        { id: 2, name: "shinzo" },
        { id: 3, name: "Chiyo" }
      ]
    }

I want to find all the updated data in newObj objects. Ex, description of oldObj is updated to "abcd" in newObj and in list name of two objects has been updated. So, my expected output is:

const extractObjDiff = {
      description: "abcd",
      list: [
        { id: 1, name: "Peter" },
        { id: 2, name: "Cathenna" }
      ]
    }

I have tried below code but it's not working for array list.

function extractObjDiff(newObj, oldObj) {
  var r = {};
  for (var prop in newObj) {
    if (!oldObj.hasOwnProperty(prop)) {
      if (Array.isArray(newObj)) {
        r = newObj;
      } else {
        r[prop] = newObj[prop];
      }
    } else if (newObj[prop] === Object(newObj[prop])) {
      var difference = newObj[prop].length !== oldObj[prop].length ? newObj[prop] : extractObjDiff(newObj[prop], oldObj[prop], []);
      if (Object.keys(difference).length > 0) r[prop] = difference;
    } else if (newObj[prop] !== oldObj[prop]) {
      if (newObj[prop] === undefined)
        r[prop] = 'undefined';
      if (newObj[prop] === null)
        r[prop] = null;
      else if (typeof newObj[prop] === 'function')
        r[prop] = 'function';
      else if (typeof newObj[prop] === 'object')
        r[prop] = 'object'
      else if (Array.isArray(newObj))
        r = newObj;
      else
        r[prop] = newObj[prop];
    }
  }
  return r;
}

Does this answer your question? [Generic deep diff between two objects](https://stackoverflow.com/questions/8572826/generic-deep-diff-between-two-objects) — ldruskis, Feb 11 '22 at 12:58
@NinaScholz - I want updated data only if that is not matching my expectation then it is of no use. — Mrityunjay Yadav, Feb 11 '22 at 13:40

score 0 · Answer 1 · answered Feb 11 '22 at 18:45

I have added 2 functions, first one give your expected output and second one give the every changes in the new object.

const newObj = {
  description: "abcd",
  type: "anything",
  list: [
    { id: 1, name: "Peter" },
    { id: 2, name: "Cathenna" },
    { id: 3, name: "Chiyo" }
  ]
};

const oldObj = {
  description: "wwew",
  type: "anything",
  list: [
    { id: 1, name: "Amara" },
    { id: 2, name: "shinzo" },
    { id: 3, name: "Chiyo" }
  ]
};

const findSubChanges = (oldObj, newObj) => {
  let changes=[]
  for (const i in oldObj) {
    if (oldObj[i] instanceof Object) {
      let isChange=false
      for (const j in oldObj[i]){
        if(oldObj[i][j] !== newObj[i][j]){
          isChange=true
          break
        }
      }
      if (isChange){
        changes[i] = newObj[i]
      }
    } else {
      if (oldObj[i] !== newObj[i]) {
        changes[i] = newObj[i];
      }
    }
  }
  return changes
};

const findChanges = (oldObj, newObj) => {
  let changes={}
  for (const i in oldObj) {
    if (oldObj[i] instanceof Object) {
      const change = findSubChanges(oldObj[i], newObj[i]);
      if (change) {
        changes[i] = change
      }
    } else {
      if (oldObj[i] !== newObj[i]) {
        changes[i] = newObj[i];
      }
    }
  }
  return changes
};

const extractObjDiff=findChanges(oldObj, newObj)
console.log(extractObjDiff);

const newObj = {
  description: "abcd",
  type: "anything",
  list: [
    { id: 1, name: "Peter" },
    { id: 2, name: "Cathenna" },
    { id: 3, name: "Chiyo" }
  ]
};

const oldObj = {
  description: "wwew",
  type: "anything",
  list: [
    { id: 1, name: "Amara" },
    { id: 2, name: "shinzo" },
    { id: 3, name: "Chiyo" }
  ]
};


const isArray = (item) => item instanceof Array;
const isJSONObject = (item) =>
  item instanceof Object && !(item instanceof Array);

const findEveryChanges = (oldObj, newObj) => {
  if (
    (isArray(oldObj) && isArray(newObj)) ||
    (isJSONObject(oldObj) && isJSONObject(newObj))
  ) {
    let changes = isArray(oldObj) ? [] : {};
    for (const i in oldObj) {
      if (oldObj[i] instanceof Object) {
        const change = findEveryChanges(oldObj[i], newObj[i]);
        if (change) {
          changes[i] = change;
        }
      } else {
        if (oldObj[i] !== newObj[i]) {
          changes[i] = newObj[i];
        }
      }
    }
    if (Object.keys(changes).length > 0) {
      return changes;
    }
    return;
  }
  if (oldObj !== newObj) {
    return newObj;
  }
  return;
};


console.log(findEveryChanges(oldObj, newObj));

How to return the difference between two Objects having array and return the difference value dynamically

1 Answers1