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

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; }

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?
@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

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Comments

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

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).

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