Compare objects recursively and put duplicate key values into array

Question

I have three objects I need to iterate to check for duplicates to end up with a single object. If there are duplicates, I'd like to put them into an array so the user can select the best value so they all ultimately end up as strings or integers (or objects with strings/integers). They might look like this:

const a = {
  first_name: 'Tom',
  height: {
    feet: 5,
    inches: 0
  }
}
const b = {
  first_name: 'Thomas',
  last_name: 'Walsh',
  email: '[email protected]',
  height: {
    feet: 6,
    inches: 0
  }
}
const c = {
  email: '[email protected]'
}

The result would look like this:

const result = {
  first_name: ['Tom', 'Thomas'],
  last_name: 'Walsh',
  email: ['[email protected]', '[email protected]'],
  height: {
    feet: [5, 6],
    inches: 0
  }
}

I have no idea if a, b, or c would be the authority on keys so I have to assume an unknown set of key/value pairs, but it's definitely small (no more than 20 pairs, only 2-3 would be more than 3 levels deep, and each of those levels would be a maximum of 4-5 key/value pairs.

I can create a new object, iterate each of the three recursively, and dump the value or create an array of values, but that seems inefficient. Any suggestions?

I've got lodash in the project if needed. Thanks!

Ori Drori · Accepted Answer · 2018-12-10 18:14:12Z

Since there are nesting keys that might be missing in some of the objects, you can merge them via lodash's _.mergeWith(), and collect duplicates into arrays:

const a = {"first_name":"Tom","height":{"feet":5,"inches":0}}
const b = {"first_name":"Thomas","last_name":"Walsh","email":"[email protected]","height":{"feet":6,"inches":0}}
const c = {"email":"[email protected]"}

const shouldCollect = (s) => _.negate(_.overSome([
  _.isUndefined,
  _.isObject,
  _.partial(_.eq, s)
]))


const mergeDupes = (...args) => _.mergeWith({}, ...args, (o, s) => {
  if(_.isArray(o)) return _.uniq([...o, s]);
  if(shouldCollect(s)(o)) return [o, s];
})

const result = mergeDupes(a, b, c)

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

If you want to remove non duplicate properties, you can then clean the object via a recursive _.transform():

const a = {"first_name":"Tom","height":{"feet":5,"inches":0}}
const b = {"first_name":"Thomas","last_name":"Walsh","email":"[email protected]","height":{"feet":6,"inches":0}}
const c = {"email":"[email protected]"}

const shouldCollect = (s) => _.negate(_.overSome([
  _.isUndefined,
  _.isObject,
  _.partial(_.eq, s)
]))

const omitNonDuplicates = obj =>
  _.transform(obj, (a, v, k) => {
    if (_.isArray(v)) a[k] = v;
    else if (_.isObject(v)) {
      const clean = omitNonDuplicates(v);
      if(!_.isEmpty(clean)) a[k] = clean;
      return;
    }
  });
  
const mergeDupes = (...args) => omitNonDuplicates(_.mergeWith({}, ...args, (o, s) => {
  if(_.isArray(o)) return _.uniq([...o, s]);
  if(shouldCollect(s)(o)) return [o, s];
}))

const result = mergeDupes(a, b, c)

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

I have to accept this as the best answer. Not only does it solve my needs, it kinda blows my mind. Thanks!

trincot · Accepted Answer · 2018-12-10 17:40:12Z

You will need a recursive function that dives into the object properties in tandem:

function mergeObjects(objs) {
    objs = objs.filter(obj => obj !== undefined);
    // return value or array when at least one of the values is a primitive
    if (objs.some(obj => Object(obj) !== obj)) { 
        objs = Array.from(new Set(objs)); // Get unique values
        return objs.length === 1 ? objs[0] : objs;
    }
    // Get all the keys
    const keys = Array.from(new Set([].concat(...objs.map(obj => Object.keys(obj))))); 
    return Object.assign({}, ...keys.map(key => 
        ({ [key]: mergeObjects(objs.map(obj => obj[key])) })));
}

// Demo:
const a = {first_name: 'Tom', height: {feet: 5,inches: 0}};
const b = {first_name: 'Thomas',last_name: 'Walsh',email: '[email protected]', height: {feet: 6,inches: 0}};
const c = {email: '[email protected]'};

const result = mergeObjects([a,b, c]);
console.log(result);

eag845 · Accepted Answer · 2018-12-10 17:43:01Z

I think there is not function to do that, you have to iterate over their properties.

const a = { first_name: 'Tom', height: {feet: 5, inches: 0 } };
const b = { first_name: 'Thomas', last_name: 'Walsh', email:'[email protected]',  height: { feet: 6, inches: 0} };
const c = { email: '[email protected]' };

let newObj = {};

[a, b, c].forEach(obj => {
    Object.entries(obj).forEach(([key, value]) => {
        if (newObj.hasOwnProperty(key)) { // if the property exist
            if (Array.isArray(newObj[key])) {
                newObj[key].push(value);
            } else {
                let temporalVal = newObj[key];
                newObj[key] = [temporalVal, value];
            }
        } else { // if the property does not exist, create it.
            newObj[key] = value;
        }
    })
});

console.log(newObj)

Nina Scholz · Accepted Answer · 2018-12-10 17:54:55Z

You could take a recursive approach by checking the values and take the nested object for inner values.

const
    merge = (a, b) => {
        Object.entries(b).forEach(([k, v]) => {
            if (v && typeof v === 'object') {
                return merge(a[k] = a[k] || {}, v);
            }
            if (!(k in a)) {
                return a[k] = v;
            }
            if ([].concat(a[k]).includes(v)) {
                return;
            }
            a[k] = [].concat(a[k], v); 
        });
        return a;
    },
    a = { first_name: 'Tom', height: { feet: 5, inches: 0 } },
    b = { first_name: 'Thomas', last_name: 'Walsh', email: '[email protected]', height: { feet: 6, inches: 0 } },
    c = { email: '[email protected]', height: { feet: 15 } },
    result = [a, b, c].reduce(merge, {});

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Akrion · Accepted Answer · 2018-12-10 23:23:59Z

0

Here is a concise recursive solution via Array.reduce and Array.forEach:

const a = { first_name: 'Tom', height: { feet: 5, inches: 0 } },
      b = { first_name: 'Thomas', last_name: 'Walsh', email: '[email protected]', height: { feet: 6, inches: 0 } },
      c = { email: '[email protected]'},
      d = { first_name: 'Tomy', height: { feet: 15, inches: 10 } }

const mergeKeys = (a,b) => {
  if(a != undefined) {
    if(a === b) return a
    if(typeof b == 'object') return merge([a,b])      
    else return [...(Array.isArray(a) ? a : [a]), b]
  } else return b
}

const merge = arr => arr.reduce((r,c) => 
  (Object.entries(c).forEach(([k,v]) => r[k] = mergeKeys(r[k],c[k])), r) ,{})

console.log(merge([a,b,c,d]))

edited Dec 10, 2018 at 23:23

answered Dec 10, 2018 at 20:47

Akrion

18.6k1 gold badge38 silver badges58 bronze badges

Comments

Yuri Gor · Accepted Answer · 2019-03-07 23:07:16Z

0

How about Lodash + Deepdash:

let merged = _.cloneDeep(objects.shift()); // clone to keep source untouched
objects.forEach((obj) => {
  _.eachDeep(obj, (value, key, parent, ctx) => {
    if (_.isObject(value)) return;
    let exists = _.get(merged, ctx.path);
    if (exists == undefined) {
      exists = value;
    } else {
      exists = _.uniq([].concat(exists, value));
      if (exists.length == 1) exists = exists[0];
    }
    _.set(merged, ctx.path, exists);
  });
});

full test for your case

edited Mar 7, 2019 at 23:07

answered Jan 21, 2019 at 20:45

Yuri Gor

1,4931 gold badge15 silver badges28 bronze badges

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