I have two objects and i need to merge them and concat strings if two props have the same key

user_9863333 0
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I have two objects and i need to merge them and concat strings if two props have the same key note: I'm using lodash.js

obj1 = {
  name: 'john', 
  address: 'cairo'
}

obj2 = {
  num : '1', 
  address: 'egypt'
}

I need the merged object to be like:

merged = {name:"john", num: "1", address:"cairo,Egypt"}

the issue with address prop when I'm trying to use _.defaults(obj1,obj2) or _.merge(obj1,obj2)

the address value will be the value of the address prop inside obj2 so I need a way to merge the two objects and concat the two address props in each object.

lodash angular typescript ecmascript-6 javascript
4 Answers

Try this:

    function merge(obj1, obj2) {
      let merged = {
        ...obj1,
        ...obj2
      };
      Object.keys(obj1).filter(k => obj2.hasOwnProperty(k)).forEach((k) => {
        merged[k] = obj1[k] + "," + obj2[k]
      })
      return merged
    }

    obj1 = {
      name: 'john',
      address: 'cairo'
    }

    obj2 = {
      num: '1',
      address: 'egypt'
    }

    console.log(merge(obj1, obj2))

user_159163610

You don't even need lodash. You can easily create you own function for that. You can do it like this:

  • new Set - to find all unique keys across both input objects
  • for...of - to iterate over unique keys calculated above

function mergeObjects(obj1, obj2) {
  let merged = {};
  for (const property of [...new Set([...Object.keys(obj1),...Object.keys(obj2)])]) {
    if(obj1[property]) merged[property] = obj1[property];
    if(obj2[property]) merged[property] = merged[property] ? `${merged[property]},${obj2[property]}` : obj2[property];
  }
  return merged;
}

const obj1 = { name: 'john', address: 'cairo' };
const obj2 = { num : '1', address: 'egypt' };

const mergedObj = mergeObjects(obj1, obj2);
console.log(mergedObj);

user_143898300 
function mergeObjects(objArr) {
    const newObj = {};

    objArr.forEach((element) => {
        const keys = Object.keys(element);
        keys.forEach((key) => {
            if (newObj[key]) newObj[key] = newObj[key] + "," + element[key];
            else newObj[key] = element[key];
        });
    });
    return newObj;
}

const obj1 = {name: 'john',   address: 'cairo'}

const obj2 = {  num : '1',   address: 'egypt'}
console.log(mergeObjects([obj1, obj2]));

This way you can merge any number of objects!

user_53270400

You can use _.mergeWith() to concat the values of specific keys to arrays, and then use _.mapValues() to join the arrays to strings:

const { mergeWith, mapValues, uniq, join } = _;

const fn = (predicate, ...objs) => mapValues(
  // merge the objects
  mergeWith(
    {}, 
    ...objs, 
    // handle the keys that you want to merge in a uniqe way
    (a = [], b = [], key) => predicate(key) ? a.concat(b) : undefined
  ),
  // transform the relevant keys' values to a uniqe strings
  (v, key) => predicate(key) ? uniq(v).join(', ') : v
);

const obj1 = { name: 'john', address: 'cairo' };
const obj2 = { num : '1', address: 'egypt' };

const result = fn(key => key === 'address', obj1, obj2);

console.log(result);
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