Javascript: Is there a cleaner way to extract object properties?

Question

I have the following JS code:

let obj1 = {
    prop1: 1,
    prop2: 2,
    prop3: 3,
    prop4: 4
}

let obj2 = {
    prop1: obj1.prop1,
    prop2: obj1.prop2,
}

Here I create obj2 which has certain select properties of obj1. Is there a cleaner/quicker way to do this than what I've done here? Some kind of destructuring hack?

`let { prop3, prop4, ...obj2 } = obj1` but that is confusing and fails if you add properties. There's no syntax for this so just create a helper function. — Aluan Haddad, Jun 06 '20 at 03:55
are you trying to clone obj1? if so I think you want to do json.parse/stringify — Rick, Jun 06 '20 at 03:56

score 2 · Answer 1 · answered Jun 06 '20 at 04:07

2

You can do this way,

let obj1 = {
    prop1: 1,
    prop2: 2,
    prop3: 3,
    prop4: 4
}

let obj2 = JSON.parse(JSON.stringify(obj1,['prop1','prop2']))
console.log(obj2)

answered Jun 06 '20 at 04:07

Narendra Chouhan

2,291
1
15
24

Divyansh Yadav · Answer 2 · 2020-06-06T04:57:01.860

1

let obj1 = {
    prop1: 1,
    prop2: 2,
    prop3: 3,
    prop4: 4
}

let { prop1, prop2 } = obj1

let obj2 = {
    prop1,
    prop2
}

console.log(obj2)

edited Jun 06 '20 at 04:57

answered Jun 06 '20 at 04:19

Divyansh Yadav

51
4

score 0 · Answer 3 · answered Jun 06 '20 at 04:13

Hi try to store all your obj1 properties to obj2. may e it will help you.

let obj1 = {
    prop1: 1,
    prop2: 2,
    prop3: 3,
    prop4: 4
}
//ES6
let obj2 = {}
for(key in obj1){
  obj2[key]= obj1[key]
}
console.log(obj2)
//ES5
let obj3 = {}
Object.keys(obj1).forEach(function(key){
  obj3[key]= obj1[key]
})
console.log(obj2)

chiragrtr · Answer 4 · 2020-06-06T04:38:11.677

JSON.stringify way is great except that won't work for functions. So, if you have function in your object, better to do this:

let obj1 = {
    prop1: function(x){console.log("hello", x)},
    prop2: 2,
    prop3: 3,
    prop4: 4
}

const keysForObj2 = ["prop1", "prop2"]

let obj2 = {};

for (key in obj1) {
    if (keysForObj2.includes(key)) {
        obj2[key] = obj1[key];
    }
}
console.log(obj2);    // Only prop2 will be present with JSON way

obj2.prop1("world"); You can't do this in JSON way

score 0 · Answer 5 · answered Jun 06 '20 at 04:23

You could get do it with a utility function I created.

let obj1 = {
  prop1: 1,
  prop2: 2,
  prop3: 3,
  prop4: 4
}

const { pick } = rubico

const obj2 = pick(['prop1', 'prop2'])(obj1)

console.log(obj2)

<script src="https://unpkg.com/rubico/index.js"></script>

Documentation for pick

Javascript: Is there a cleaner way to extract object properties?

5 Answers5