Javascript removing an object element from an array in a clean way (not leaving a null ghost)

Question

I have an array:

var Array = {};
Array['elements'] = [];
Array['elements'][0]['name'] = "Sally";
Array['elements'][0]['age'] = "20";
Array['elements'][3]['name'] = "Jack";
Array['elements'][3]['age'] = "21";
Array['elements'][4]['name'] = "Megan";
Array['elements'][4]['age'] = "22";

I do not know how to remove Jack from the array to return a list of women only. Splice is mutable, and passing back the entire object seems inefficient, and cumbersome.

In PHP, you can:

unset($Array['elements'][3]);

I have tried

delete Array['elements'][3];

but that just yields a null value in its place, not really deleting the element, messing up everywhere else I am testing for elements. Is there a clean way to delete an element from an array based on its key?

Thanks!

Your code as written doesn't work since Array.elements[0] [3] and [4] are never defined, you can't add properties to them - firstly, I'd never overload Array, I wouldn't call that variable any variation of Array since it's not an Array; and finally just test for null if you insist on .elements being an Array (you could make it an Object instead, and you won't end up with a sparse array) — Bravo
– Bravo, Commented Oct 12, 2019 at 2:38
why are you adding to indices 0, 3 and 4 only? What is the significance of these numbers? — Bravo
– Bravo, Commented Oct 12, 2019 at 2:43

dinakajoy · Accepted Answer · 2019-10-12 02:55:41Z

1

Try this, it uses splice though but it will leave your initial array as it is -

let array = [];
array.push({name:'Sally', age:20});
array.push({name:'Jack', age:21});
array.push({name:'Megan', age:22});
let newArray = [...array];
newArray.splice(1, 1);

Check this article https://jaketrent.com/post/remove-array-element-without-mutating/

answered Oct 12, 2019 at 2:55

dinakajoy

1342 silver badges7 bronze badges

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

Comments

Bravo · Accepted Answer · 2019-10-12 03:09:08Z

Firstly, don't use Array as an variable name - it is the javascript Array object, you don't want to override that

Secondly, since Array = {}, calling it any variation of the word Array is misleading, it's an Object

Thirdly, you've created Array.elements as an array, but then populate only indices 0, 3, and 4 - so you've created a sparse array to begin with

Fourthly, the code you wrote doesn't even run, since you are trying to assign .name to elements[0] but at that point elements[0] is undefined, so you'll end up with an error, and the code stops running right there

What it looks like you want is Array.elements = {} - then you can add/delete any key you want

For example

var obj = {};
obj.elements = {};
obj.elements[0] = {};
obj.elements[0].name = "Sally";
obj.elements[0].age = "20";
obj.elements[3] = {};
obj.elements[3].name = "Jack";
obj.elements[3].age = "21";
obj.elements[4] = {};
obj.elements[4].name = "Megan";
obj.elements[4].age = "22";

delete obj.elements[3];

for (let i in obj.elements) {
    console.log('Number', i, 'is', obj.elements[i].name);
}

When using elements as an Array, you'll see after your initial population of the array, you already have two undefined to begin with - see first console output

Note: however, for...in loop will skip those undefined elements

Also note, the undefined elements are actually "empty slots" - i.e. if you simply put obj.elements[3] = undefined that's not the same as delete obj.elements[3]

var obj = {};
obj.elements = [];
obj.elements[0] = {};
obj.elements[0].name = "Sally";
obj.elements[0].age = "20";
obj.elements[3] = {};
obj.elements[3].name = "Jack";
obj.elements[3].age = "21";
obj.elements[4] = {};
obj.elements[4].name = "Megan";
obj.elements[4].age = "22";

console.log(obj.elements)

delete obj.elements[3];

console.log(obj.elements)
for (let i in obj.elements) {
    console.log('Number', i, 'is', obj.elements[i].name);
}

Leslie · Accepted Answer · 2019-10-12 03:43:19Z

1

if you want to remove Jack from the array, you can code like this:

Array['elements'].filter(e => e.name != 'Jack');

answered Oct 12, 2019 at 3:43

Leslie

412 bronze badges

Comments

svidgen · Accepted Answer · 2019-10-12 03:02:12Z

0

You can remove items from an array by splicing it:

var a = [1,2,3,4,5]
var removed = a.splice(1,2)

a becomes:

[1,4,5]

And removed contains:

[2,3]

You can select a new, filtered list by referring to Nidhin's answer.

^{As an aside, the code in your question is not JavaScript... Are you running that gibberish successfully somewhere?}

edited Oct 12, 2019 at 3:02

answered Oct 12, 2019 at 2:40

svidgen

14.4k4 gold badges37 silver badges60 bronze badges

5 Comments

Bravo Over a year ago

then the indices for the entries will change

svidgen Over a year ago

@Bravo Yes ... is that not the intention?

Nidhin Joseph Over a year ago

@svidgen Are you running that gibberish successfully somewhere? haha :D :D

Bravo Over a year ago

@svidgen - since the initial attempt creates a sparse array, not sure what the intention is - it seems the indices are important (should use an object instead0

svidgen Over a year ago

@Bravo Yeah, I'd read it as the indexes being incidental. But, you may be right. Post an answer!!!

Collectives™ on Stack Overflow

Javascript removing an object element from an array in a clean way (not leaving a null ghost)

4 Answers 4

Comments

Comments

Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related