Update a JSON formatted JavaScript object based on another

Question

Having two JSON formatted js-objects:

obj1 = { prop1: 1,
         prop2: 2,
         prop3: 3 }

obj2 = { prop1: 1,
         prop2: 3 }

What is the best js-practise to update obj2 into obj1, that also removes properties? Typically in a jQuery/angular context. Resulting in:

obj1 = { prop1: 1,   // not updated, nor overwritten
         prop2: 3    // updated
       }             // prop3 removed

Must also deal with nested objects and arrays.

If you are deleting the properties not present in obj2 from obj1. Then you always ending up with obj2. What i mean is that resulting json will always be obj2 irrespective of what obj1 has. Could you please provide a better example. — Cyril Cherian
– Cyril Cherian, Commented Jun 5, 2015 at 10:22
I have been looking into both jquery's and angular's extend functions, but these does not delete removed properties. — ralftar
– ralftar, Commented Jun 5, 2015 at 10:22
What @CyrilCherian is trying to say is that it sounds illogical what you're trying to do, because you can actually just type: obj1 = obj2; and will do what you asked. — Ivanka Todorova
– Ivanka Todorova, Commented Jun 5, 2015 at 10:25
That is correct, Cyril Cheria. But then obj1 is changed to obj2. I need to keep obj1 since it has attached listeners. — ralftar
– ralftar, Commented Jun 5, 2015 at 10:26
Can't you just reattach the listeners? Can you update your question with another example or deeper explanation about what you're trying to do? — Ivanka Todorova
– Ivanka Todorova, Commented Jun 5, 2015 at 10:30

Cyril Cherian · Accepted Answer · 2015-06-05 10:42:09Z

1

Try this:

function merge_objects(obj1,obj2){
    for (var attr in obj2) { obj1[attr] = obj2[attr]; }
    for (var attr in obj1) { if(!obj2[attr]){ delete obj1[attr]} }
    return obj1;
}

answered Jun 5, 2015 at 10:42

Cyril Cherian

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2 Comments

Octav Zlatior Over a year ago

This should work, with two comments: don't forget to check for hasOwnProperty and watch out for the case obj2 has the property "attr" but it is "false" or "undefined" or 0: your condition will evaluate to "true" and the property will be deleted from obj1... try something like if (!(obj2.hasOwnProperty(attr))) { delete obj1[attr] } instead :)

ralftar Over a year ago

Thanks Cyril and Octav. I'll go with a recursive version of this.

kTT · Accepted Answer · 2015-06-05 10:19:15Z

1

To compare objects you can use angular.equals(obj1, obj2). For merging you can check angular.extend but it won't delete missing elements.

answered Jun 5, 2015 at 10:19

kTT

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Comments

Murthy · Accepted Answer · 2015-06-05 11:26:27Z

0

If you want to copy(or clone including arrays/child objects) contents of object2 into object1, try using jquery extend()

Please find jsfiddle [here][2]

answered Jun 5, 2015 at 11:26

Murthy

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