CODEWITHSUNDEEP
javascriptlodash
karthick
karthick

Reputation: 6168

How to merge object - lodash?

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

Upvotes: 1

Views: 433

Answers (2)

user3297291
user3297291

Reputation: 23382

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.

Upvotes: 1

gurvinder372
gurvinder372

Reputation: 68393

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)

Upvotes: 1

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