Replace object value with other object's value of the same key with JavaScript

Question

I've got two objects, item and results. They've both got the same keys but possibly different values, for example:

item.id = '50'
item.area = 'Mexico'
item.gender = null
item.birthdate = null

results.id = '50'
results.area = null
results.gender = 'Male' 
results.birthdate = null

What I want to do is exactly the following:

if (item.id == null || items.id == 0)
{
    item.id = results.id;
}

but I'm looking for a way to do this for each value of my item object. You know, without having to write a huge function if my objects happen to have a lot more keys / values. Any ideas?

Update : I misunderstood my own problem and the only issue was that I didnt really understand how to get an object value given a certain key. I couldnt really use any outside scripts or divs since Im using Azure's mobile service scripts.

for (var key in item) {
    if(item[key] == null || item[key] == 0){
        item[key] = results[0][key] 
    }             
}

Loop over the object. Or if you are using jQuery, look at merge. — epascarello, Oct 09 '15 at 15:04
Possible duplicate of [Loop through JavaScript object](http://stackoverflow.com/questions/684672/loop-through-javascript-object) — Bartek Banachewicz, Oct 09 '15 at 15:05
You could do this using angulars `$filter`, or using lodash, or using the native `.map`. Choose your poison! — Darth Egregious, Oct 09 '15 at 15:06
@BartekBanachewicz Thanks you were right. I saw that question before but misunderstood my own problem. — Luuk Gortzak, Oct 12 '15 at 08:01

Anonymous0day · Accepted Answer · 2015-10-12T08:02:51.870

It could do the trick !

var item = {};
var results={};

item.id = '50'
item.area = 'Mexico'
item.gender = null
item.birthdate = null

results.id = '50'
results.area = null
results.gender = 'Male'
results.birthdate = null

Object.keys(item).forEach(function(key) {
  if (item[key] == null || item[key] == 0) {
    item[key] = results[key];
  }
})
document.getElementById('dbg').innerHTML ='<pre>' + JSON.stringify(item , null , ' ') + '</pre>';

console.dir(item);

<div id='dbg'></div>

score 4 · Answer 2 · answered Oct 09 '15 at 15:13

You can elegantly use lodash:

var results = {};
var item = {};

item.id = '50';
item.area = 'Mexico';
item.gender = null;
item.birthdate = null;

results.id = '50';
results.area = null;
results.gender = 'Male'; 
results.birthdate = null;

_.merge(results, _.pick(item, _.identity));

alert(JSON.stringify(results));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.10.1/lodash.js"></script>

Note that the requested value is now in results (and not in item). If you still need it item, clone the values into a new variable and use it.

lodash is very helpful library when working with arrays and objects. — maverick, Jul 18 '21 at 17:30

score 2 · Answer 3 · answered Oct 09 '15 at 15:07

You can loop over the object like this. hasOwnProperty tests if it is a property defined by you and not from the base object definition.

for (var key in item) {
   if (item.hasOwnProperty(key)) {
       if (item[key] == null) {
           item[key] = results[key];
       }
   }
}

score 2 · Answer 4 · answered Mar 17 '21 at 14:24

Old post but if you search a more recent straightforward solution you can try Object.assign(). Properties in the target object are overwritten by properties in the sources if they have the same key.

const target = { a: 1, b: 2 };
const source = { b: 4, c: 5 };

const returnedTarget = Object.assign(target, source);

console.log(target);
// expected output: Object { a: 1, b: 4, c: 5 }

console.log(returnedTarget);
// expected output: Object { a: 1, b: 4, c: 5 }

score 1 · Answer 5 · answered Mar 09 '21 at 15:33

You can also use the nullish coalescing operator to simplify it a bit.

var item = {
  id: '50',
  area: 'Mexico',
  gender: null,
  birthdate: null
};
var results={
  id: '50',
  area: null,
  gender: 'Male',
  birthdate: null
};

Object.keys(item).forEach(function(key) {
  item[key] = item[key] ?? results[key];
})

document.getElementById('dbg').innerHTML ='<pre>' + JSON.stringify(item , null , ' ') + '</pre>';

console.dir(item);

<div id='dbg'></div>

score 1 · Answer 6 · answered Jan 10 '22 at 19:47

1

For the one liner, here is an option:

{ ...item, ...Object.keys(results).reduce((pv, cv) => results[cv] == null ? pv : { ...pv, [cv]: results[cv] }, {}) };

answered Jan 10 '22 at 19:47

Cappa

107
1
6

score 0 · Answer 7 · edited Nov 30 '17 at 12:23

0

You could just iterate all the object keys, and then write assign them on each item:

for (var property in results) {
    if (results.hasOwnProperty(property) && !item[property]) {
        // do stuff
        item[property] = results[property]
    }
}

edited Nov 30 '17 at 12:23

geisterfurz007

5,292
5
33
54

answered Oct 09 '15 at 15:05

Dory Zidon

10,497
2
25
39

Replace object value with other object's value of the same key with JavaScript

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