How to merge objects?

Question

For instance, from these two objects :

var object1 = {
  "color": "yellow",
  "size": null,
  "age": 7,
  "weight": null
}

var object2 = {
  "color": "blue",
  "size": 51,
  "age": null
}

I want this (object2 overrides object1 except for null properties or properties he doesn't have):

{
  "color": "blue",
  "size": 51,
  "age": 7,
  "weight": null
}

Answer 1

Copy

var src = { name: 'Apple', price: 5};
var dst= angular.copy(src);

• deep copy

Extend:

var mergedObject = angular.extend(dst, src1, src2, ...) 

• shallow copy

Merge:

var mergedObject = angular.merge(dst, src);

• since angular 1.4+
• deep (recursively) copy

If you want to not overwrite with null, you can use this.

---

Object.assign():

let movie2 = Object.assign({}, movie1, { episode: 8 });

• fot Angular 2+ (ECMAScript 6)

Sources:

• https://docs.angularjs.org/api/ng/function

• http://davidcai.github.io/blog/posts/copy-vs-extend-vs-merge/

Answer 2

For newer versions (at least 1.4.0) of angular you can use angular.merge

Unlike extend(), merge() recursively descends into object properties of source objects, performing a deep copy.

Answer 3

Using angualr.extend will not produce the result requested. The object2.age null value will override object1.age value.

angular.extend(object1, object2) will produce the following result:

{
    "color" : "blue", 
    "size" : 51, 
    "age" : null,   <=== undesirable result
    "weight" : null
}

Use the following code to skip over null properties

for (var prop in object1) {
    if(object1.hasOwnProperty(prop) && object2.hasOwnProperty(prop) && object2[prop]!=null) {
        object1[prop] = object2[prop];
    }
}

This will produce the following requested result

{
    "color" : "blue", 
    "size" : 51, 
    "age" : 7, 
    "weight" : null
}