How do you merge two javascript objects

Question

I have one object like this

let ob1 = {
'item_data':{
  'stack':{
    'purchase':'12345',
    'order':'22222'
   }
  }
}

and another object like this

let ob2 = {
  'stack':{
    'purchase':'444444'
   }
 }

The resultant object should look like this

result = {
  'item_data':{
    'stack':{
      'purchase':'444444',
      'order':'22222'
     }
   }
 }

The code is in a nodejs application. I am wondering if there is any javascript library to do this kind of merge/replace objects in server side js.

Thanks for helping.

I tried this `let d = Object.assign(ob1['item_data'], ob2 );` and it produce this result `{ stack: { purchase: '444444' } }` — Know Nothing, Jan 16 '18 at 18:13

score 1 · Accepted Answer · answered Jan 16 '18 at 18:35

There are quite a few npm packages out there to accomplish this, but one that is very popular is lodash.merge.

Take a look at the lodash merge function: https://lodash.com/docs/4.17.4#merge

This method is like _.assign except that it recursively merges own and inherited enumerable string keyed properties of source objects into the destination object. Source properties that resolve to undefined are skipped if a destination value exists. Array and plain object properties are merged recursively. Other objects and value types are overridden by assignment. Source objects are applied from left to right. Subsequent sources overwrite property assignments of previous sources.

And an example:

var object = {
  'a': [{ 'b': 2 }, { 'd': 4 }]
};
var other = {
  'a': [{ 'c': 3 }, { 'e': 5 }]
};

_.merge(object, other);
// => { 'a': [{ 'b': 2, 'c': 3 }, { 'd': 4, 'e': 5 }] }

Use the lodash.merge npm package to pull in just this method: https://www.npmjs.com/package/lodash.merge

Good luck!

An additional note about `Object.assign`: It will only copy the top level property values over, so it won't by default do the "deep merge" illustrated in the question. We would need to create a recursive function to iterate and `Object.assign` each property in order for it to work. Leaning on others code like `lodash.merge` is going to be more convenient and less prone to corner case errors since its well used. — Flet, Jan 16 '18 at 18:37

score 0 · Answer 2 · answered Jan 16 '18 at 18:23

This is what you want.

let ob1 = {
'item_data':{
  'stack':{
    'purchase':'12345',
    'order':'22222'
   }
  }
}
// and another object like this

let ob2 = {
  'stack':{
    'purchase':'444444'
   }
 }
Object.assign(ob1.item_data.stack, ob2.stack);
console.log(ob1);

score 0 · Answer 3 · answered Jan 16 '18 at 18:25

0

Try this:

function merge(a, b) {
    for (var key in b) {
        if (exports.merge.call(b, key) && b[key]) {
            if ('object' === typeof (b[key])) {
                if ('undefined' === typeof (a[key])) a[key] = {};
                exports.merge(a[key], b[key]);
            } else {
                a[key] = b[key];
            }
        }
    }
    return a;
}
merge(obj1, obj2);

answered Jan 16 '18 at 18:25

HOTAM SINGH

121
2
11

Why to use so complex function if that can be done by one line `Object.assign` . – Himanshu sharma Jan 16 '18 at 18:27
found this one https://www.npmjs.com/package/merge and seems working . Thank you everyone for prompt response. – Know Nothing Jan 16 '18 at 18:36

How do you merge two javascript objects

3 Answers3