How to add and remove elements of an Array

Question

I want to maintain a list of things in javascript. This seems to be a non trivial problem in this language...

var things = []

// for adding:
things[things.length] = thing

// for removing:
delete (things[things.indexOf(thing)])

This kinda works, but I fear the adding is a bug. When a thing that is not at the end of the array gets removed, a following add operation will overwrite an existing element, right? Because length is the number of elements.

How to do the adding correctly? Or is there a better way to do this with plain javascript (no JQuery)?

Have a read through all of the [available `Array.prototype` methods](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array). You will find better ways to achieve both of those things. — James Allardice, Jun 26 '14 at 14:33
[`push()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push) and [`splice()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice). — Sirko, Jun 26 '14 at 14:33
possible duplicate of [JavaScript Array Delete Elements](http://stackoverflow.com/questions/500606/javascript-array-delete-elements) — tcooc, Jun 26 '14 at 14:35
This is not a duplicate of the referenced question as it asks about adding and removing elements from an array. — Cameron Tinker, Jun 26 '14 at 14:43
@JamesAllardice I didn't, sorry. All I found were weird solutions like the one I posted, or someone was even setting elements to 0 for "removing". — typ1232, Jun 26 '14 at 14:47

score 1 · Answer 1 · answered Jun 26 '14 at 14:33

1

For adding you want to use push, so things.push(yourThing);

answered Jun 26 '14 at 14:33

n0wak

76
3

Cameron Tinker · Accepted Answer · 2014-06-26T14:40:06.333

1

I would recommend using push and splice. With push, you don't have to keep track of your last inserted index. Also, with splice, you actually remove the element from the array and you aren't just deleting the reference and making it null.

Something like this would work:

things.push(thing);
things.splice(index, 1);

edited Jun 26 '14 at 14:40

answered Jun 26 '14 at 14:33

Cameron Tinker

9,634
10
46
85

score 1 · Answer 3 · answered Jun 26 '14 at 14:33

1

Adding to an array:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/push

Removing from an array:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice

answered Jun 26 '14 at 14:33

Hayes

848
4
10

score -1 · Answer 4 · answered Jun 26 '14 at 14:41

-1

I would use a loop.

var index;
var things= [];
for (index = 0; index < things.length; ++index) {
    text += things[index];
}

answered Jun 26 '14 at 14:41

Izekid

177
6

How does this answer the question? – Cameron Tinker Jun 26 '14 at 14:41
1

Yes, this does not answer my question. You could add some if clause that would check if the element exists and then insert there, but I don't know if that is possible. This would have the advantage of defragmentation of indices. – typ1232 Jun 26 '14 at 14:49
did not understand your question then. – Izekid Jun 26 '14 at 14:54

How to add and remove elements of an Array

4 Answers4