Delete a value from array if exist or if no exist push it to array

Question

I have a array define like :

selectedDocumentID = [];

Next i have function when i get the ID, and other function where i give the id as parameter. When i click in element with id this id is going to this modifyArray. Next i check the id using console.log (its working and i get id). After that i create a new array list that include a selectedDocument array. (it work). And i want to push to list a id if it not exist or if exist just slice it from list...

modifyArray(id) {
  let selectedDocumentID = [];

  let id = 10;

  console.log('this is: ' + id);
  console.log(this.selectedDocumentID);
  let list = this.selectedDocumentID;

  let index = list.findIndex( x => x === id);
  console.log(index);
  if (index !== id) {
    list.push(id);
    console.log(list);
    this.selectedDocumentID = list;
  }
  else {
    list = list.slice(list.indexOf(id));
    console.log(list);
    this.selectedDocumentID = list;
  }
}

So for exmaple. I click for document with id 2,4,5,6.

My selectedDocumentID = [2,4,5,6] and list also have [2,4,5,6].

Next i click to document with id 8 and my arrays = [2,4,5,6,8], after that i click to document with id 5 and my arrays you look like [2,4,6,8]. What i am doing wrong?

Code sample:

When you click document with id 5 you get [2,4,6,8]. Isn't that what you want? — Ankit Agarwal
– Ankit Agarwal, Commented Dec 29, 2017 at 8:03

ns16 · Accepted Answer · 2020-02-18 14:39:54Z

5

You can use xor lodash function to make your code simpler. For example:

modifyArray(id) {
  this.selectedDocumentID = _.xor(this.selectedDocumentID, [id]);
}

answered Feb 18, 2020 at 14:39

ns16

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1 Comment

Lorik Over a year ago

Thank you so much for this gem, it's insane what you can do if you know how data structures/statistical mathematics works.

santosh singh · Accepted Answer · 2017-12-29 08:40:09Z

2

you can try following code snippet

var index = list.findIndex(x => x==id)
// here you can check specific property for an object whether it exist in your array or not

if (index === -1){
    list.push(id);
}
else console.log("object already exists")

Update The problem in your code is that you are overriding the list

modifyArray(id) {
  let selectedDocumentID = [];

  let id = 10;

  console.log('this is: ' + id);
  console.log(this.selectedDocumentID);
  let list = this.selectedDocumentID;

  let index = list.findIndex( x => x === id);
  console.log(index);
  if (index !== id) {
    list.push(id);
    console.log(list);
    this.selectedDocumentID = list;
  }
  else {
  list.slice(list.indexOf(id));
    console.log(list);
    this.selectedDocumentID = list;
  }
}

edited Dec 29, 2017 at 8:40

answered Dec 29, 2017 at 8:07

santosh singh

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5 Comments

Tomasz Jeznach Over a year ago

Please look now at Code Sample :) I tried this way and when i try delete only '5', i get [5,6,8]. And this dont slice 5, but 2 and 3 from array :/

santosh singh Over a year ago

you can use slice operator list.splice(index,1)

Tomasz Jeznach Over a year ago

If i write there index,1 i got empty array

santosh singh Over a year ago

splice method return the item removed from array

Tomasz Jeznach Over a year ago

Also i removed list, and work only at this.selectedDocumentID for not duplicate the same value :P You help me a lot :) And replace slice for a splice. With splice its work as is should :)

Poul Kruijt · Accepted Answer · 2017-12-29 08:03:13Z

1

You have to use splice to remove:

list.splice(index, 1);

slice just extracts a portion, which I guess you can also use, but then like this:

list = list.slice(index, index + 1);

answered Dec 29, 2017 at 8:03

Poul Kruijt

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Comments

Deepu Reghunath · Accepted Answer · 2017-12-29 09:48:20Z

1

You can achieve this by javascript also

var tag_story = [];
function checkElemet()
{  
  var  id_tag = document.getElementById("ele").value,
    position = tag_story.indexOf(id_tag); 
  if ( ~position ) tag_story.splice(position, 1);
  else tag_story.push(id_tag);
  console.log(tag_story);
}

<input id="ele" type="text" placeholder="Enter Value"/>
<input type="button" onclick="checkElemet()" value="check"/>

answered Dec 29, 2017 at 9:48

Deepu Reghunath

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