Replace objects inside an array with array key

Question

I am not sure if this is a bug from my application, but I have an array like this:

var arr = [{name: 'John'}, {name: 'Jane'}, {name: 'Smith'}, {name: 'George'}];

I am trying to replace {name: 'Jane'} with {name: 'Simon'} so, I am doing

arr.splice(1, 0, {name:'Simon'})

But Jane isn't removed. Just Simon is added to the list.

I thought the splice's first arg was where to place the new array, and 0 was to replace the existing array

var arr = [{
  name: 'John'
}, {
  name: 'Jane'
}, {
  name: 'Smith'
}, {
  name: 'George'
}];



arr.splice(1, 0, {
  name: 'Simon'
})
console.log(arr)

"I thought the splice's first arg was where to place the new array, and 0 was to replace the existing array" Nope :-) developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… The argument is where to make changes. The second is how many elements to delete at that location. So you want 1, not 0, as the second argument if you want to delete the entry that's at the index. But as Nina points out below, it makes no sense to use splice to replace the entry at a given location. — T.J. Crowder
– T.J. Crowder, Commented Oct 13, 2017 at 12:58
I hope this guide can help you javascripttutorial.net/javascript-array-splice — user-developer
– user-developer, Commented Oct 13, 2017 at 13:00
Can't believe I spent half day over this. thanks @T.J.Crowder and chandra — hidar
– hidar, Commented Oct 13, 2017 at 13:08

Nina Scholz · Accepted Answer · 2017-10-13 13:05:28Z

4

Array#splice is the wrong tool, because it deletes and/or inserts elements.

You could use the index directly and replace the item.

var array = [{ name: 'John' }, { name: 'Jane' }, { name: 'Smith' }, { name: 'George' }];

array[1] = { name: 'Simon' };

console.log(array);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Edit, nearly, you could remove the actual item and add a new one, but this is in this case not advisable, because you take some array oreations, which are not necessay, like removing and inserting of an item.

arr.splice(1, 1, { name:'Simon' })
//            ^                    take one element out at index 1 and insert a new object

var array = [{ name: 'John' }, { name: 'Jane' }, { name: 'Smith' }, { name: 'George' }];

array.splice(1, 1, { name: 'Simon' });

console.log(array);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Oct 13, 2017 at 13:05

answered Oct 13, 2017 at 12:58

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

hidar Over a year ago

For some reason this does not work. the code I provided above is a sample one, I have another code but the array/object structure is the same as I have provided and yet this does not change the array, only the splice does it. Is there any reason why the splice method works (to insert) but not this?

Nina Scholz Over a year ago

@hidar, without knowing of your code, i can not give any advice.

Makla · Accepted Answer · 2017-10-13 13:01:13Z

1

Or if you just want to change the name:

arr[1].name = "Simon";

answered Oct 13, 2017 at 13:01

Makla

10.6k19 gold badges81 silver badges156 bronze badges

Comments

Dev Oskii · Accepted Answer · 2017-10-13 13:01:21Z

1

You can access elements directly by using sqaure brackets.

arr[0] will access the first element in the array so you need arr[1].

You can simply say arr[1] = {name:'Simon'}; to do this

The splice() method adds/removes items to/from an array, and returns the removed item(s).

answered Oct 13, 2017 at 13:01

Dev Oskii

92913 silver badges28 bronze badges

Collectives™ on Stack Overflow

Replace objects inside an array with array key

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related