How to merge object - lodash?

Question

I am recently started using lodash, I want to merge following objects.

Object:

var firstObj =

{
   "1" : [
           {
             name: "karthick",
             age : 25
           },

           {
             name: "arun",
             age : 20
            }
         ],
    "2" : [
           {
             name: "varun",
             age : 25
           },

           {
             name: "smith",
             age : 20
            }
         ]
}

var secondObj =

{
   "1" : [
           {
             name: "gautham",
             age : 17
           },

           {
             name: "mathan",
             age : 19
            }
         ],
    "2" : [
           {
             name: "ashok",
             age : 16
           },

           {
             name: "dharani",
             age : 20
            }
         ]
}

Merged Object / Result:

{
   "1" : [
           {
             name: "karthick",
             age : 25
           },

           {
             name: "arun",
             age : 20
            },
           {
             name: "gautham",
             age : 17
           },

           {
             name: "mathan",
             age : 19
            }
        ]
    "2" : [
           {
             name: "varun",
             age : 25
           },

           {
             name: "smith",
             age : 20
            },
           {
             name: "ashok",
             age : 16
           },

           {
             name: "dharani",
             age : 20
            }
        ]
}

What i had tried:

Fiddle

Any suggestion will be grateful

user3297291 · Accepted Answer · 2016-04-05 07:32:43Z

In the documentation you can read you have to use a customizer function that concats the arrays for you. (https://lodash.com/docs#mergeWith)

This method looks like this:

function customizer(objValue, srcValue) {
  if (_.isArray(objValue)) {
    return objValue.concat(srcValue);
  }
}

Here's it used in your example:

https://jsfiddle.net/82koarwq/

If you want to better understand what's happening inside the merge method:

Merge takes the first object that it is passed as a base. It then loops through all the keys in the other objects it is passed (in order of arguments). It does two things:

If the first object does not contain the key, it adds the key and its value.
If the first object already contains the key, it overwrites its value.

By using mergeWith, you have the opportunity to overwrite this behavior. You can pass a method that is used to deal with the second case. If you want to fall back on the default merge behavior, you'll have to make your method return undefined.

gurvinder372 · Accepted Answer · 2016-04-05 07:24:38Z

1

Try this updated fiddle

var output = {};
var firstObjKeys = Object.keys(firstObj);
var secondObjKeys = Object.keys(secondObj).filter(function(val){
  return firstObjKeys.indexOf(val) == -1;
});

var allKeys = firstObjKeys.concat(secondObjKeys);
allKeys.forEach(function(val){
  var firstArr = firstObj[val] || [];
  var secondArr = secondObj[val] || [];
  output[val] = firstArr.concat(secondArr);
})
document.body.innerHTML += JSON.stringify(output,0,4)

answered Apr 5, 2016 at 7:24

gurvinder372

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How to merge object - lodash?

Object:

var firstObj =

var secondObj =

Merged Object / Result:

What i had tried:

2 Answers 2

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Collectives™ on Stack Overflow

Object:

var firstObj =

var secondObj =

Merged Object / Result:

What i had tried:

2 Answers 2

Comments

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